[00:00.000 --> 00:02.000]  But we had equipment to sort out.
[00:02.200 --> 00:11.400]  This next is Law Enforcement Wiretaps Background and Vulnerabilities with numbers 91, 40, 123, and 90.
[00:14.850 --> 00:17.050]  I'm not a number, I'm a free man.
[00:21.050 --> 00:27.270]  So, this is a talk about how law enforcement wiretaps actually work.
[00:27.890 --> 00:33.930]  I'm Matt Blaze, this is Sandy Clark, Micah Sherr, and Eric Cronin.
[00:34.250 --> 00:36.010]  We're at the University of Pennsylvania.
[00:36.510 --> 00:41.050]  Most of this work has been published already, but it's also available on the web.
[00:41.850 --> 01:04.550]  So, what we're really looking at is the question of, not how can you wiretap somebody, but a slightly different question than the one one usually asks, which is, if law enforcement or somebody who's doing wiretaps to create a legal record of what's going on are trying to use technology to do this,
[01:04.890 --> 01:06.850]  how might that technology fail?
[01:07.130 --> 01:19.690]  That is, not how could you defeat a wiretap in theory, but based on the actual technology that law enforcement agencies are using to do wiretapping, how might that fail?
[01:19.690 --> 01:21.630]  Are there vulnerabilities in these systems?
[01:21.910 --> 01:30.310]  Now, of course, all of us as hackers know that, you know, without even looking at the technology, we know the answer is yes, because all complicated systems have bugs in them.
[01:30.690 --> 01:33.850]  But these are systems that haven't really been scrutinized very much.
[01:34.030 --> 01:48.010]  And we think we may be the first people, at least in the open community, to have gotten a hold of law enforcement wiretap systems and really scrutinized them to find out whether the records they're collecting are, in fact, accurate.
[01:48.870 --> 01:53.170]  So, just a quick primer on wiretap law in the U.S.
[01:53.570 --> 01:58.390]  Basically, law enforcement agencies do two kinds of wiretaps under the law.
[01:58.650 --> 02:02.550]  The law says there are really these two broad categories of wiretaps you can do.
[02:02.750 --> 02:12.210]  One's called a pen register, and that's a kind of wiretap that's intended to be the least intrusive kind, where they just find out what numbers you're calling.
[02:12.530 --> 02:16.430]  There's an analogous thing called a trap and trace, where they find out what numbers called you.
[02:17.310 --> 02:20.850]  It's a relatively low legal barrier to get one of these things.
[02:21.010 --> 02:26.830]  Basically, all they have to do is kind of sneeze, and then they can get a wiretap order of a pen register kind against you.
[02:27.070 --> 02:43.890]  If they actually have probable cause that you might be committing a crime, they can get out what's called a title 3 wiretap, or a full content wiretap, where they don't just find out what digits you're dialing, but they also get to listen to your phone calls.
[02:44.510 --> 02:51.630]  And that's not just a higher legal standard, but it also means somebody has to sit there and listen to the calls.
[02:51.910 --> 03:00.170]  So, according to the published statistics on wiretaps, most wiretaps are of the pen register kind, not the full content kind.
[03:00.550 --> 03:08.870]  Now, interestingly, from a technological point of view, this distinction is meaningless, because they use the same technology to implement both.
[03:09.310 --> 03:14.250]  They just turn off the record audio feature when they have just a pen register wiretap.
[03:14.430 --> 03:18.390]  So, they use the same basic equipment to do both kinds of taps.
[03:19.490 --> 03:22.770]  Now, there are a bunch of different ways they can do this.
[03:22.930 --> 03:25.830]  One is to ask the telephone company for the records of who you call.
[03:26.150 --> 03:28.850]  That only helps them with kind of your past traffic.
[03:29.010 --> 03:30.510]  It doesn't give them real-time access.
[03:31.430 --> 03:47.710]  Another way they can do this is with a technology called a loop extender, in which they basically physically hook up something to your phone line, and it basically makes a copy of everything on your phone line and sends it back to headquarters on what they call,
[03:47.810 --> 03:55.310]  in law enforcement terminology, a second friendly line that goes from your phone line back to the law enforcement agency.
[03:55.690 --> 03:57.770]  That technology is about 50 years old.
[03:57.870 --> 03:58.750]  It's still in use.
[03:58.750 --> 04:02.790]  But it's been largely supplanted in the U.S.
[04:02.950 --> 04:17.230]  by a standard interface that in the 1990s phone companies were required to have, called CALEA, or the JSTD25A, which basically is a standard wiretapping spying interface that has to be built into every phone switch.
[04:17.830 --> 04:25.430]  And it's also, again, used for both full audio taps and for just the pen register taps.
[04:25.910 --> 04:38.130]  Now, interestingly, because law enforcement agencies have all this tape recording equipment, one of the pressures on them was to keep CALEA systems compatible with the older systems.
[04:38.410 --> 04:42.230]  Now, we all know that compatibility means compatibility with all the old bugs.
[04:42.690 --> 04:51.610]  So it turns out that a lot of what we're going to talk about about loop extenders will apply to CALEA systems because they have bug compatibility built into it.
[04:52.410 --> 04:56.670]  So just a quick review for those of you who aren't telephone enthusiasts.
[04:57.010 --> 04:59.710]  This will be new for those of you who are telephone enthusiasts.
[05:00.210 --> 05:09.230]  You know, basically, the POTS telephone system aims to provide a kind of this idea of a pipe between two telephones.
[05:09.610 --> 05:14.690]  We crypto people call them Alice and Bob, but you can use any names you want for the two phones.
[05:15.170 --> 05:22.190]  If Alice wants to call Bob, she basically signals over a dedicated circuit to her central office.
[05:22.390 --> 05:25.250]  The central office decodes the dialing signals.
[05:25.870 --> 05:27.990]  Calls Bob's central office.
[05:28.190 --> 05:30.630]  Bob's central office rings Bob's phone.
[05:31.190 --> 05:34.010]  And they get kind of this virtual circuit while it's going on.
[05:34.370 --> 05:37.110]  We'll talk about how that's implemented a little more.
[05:37.510 --> 05:47.590]  But just very briefly, the interface between you and the telephone company is this thing that's about a hundred years old.
[05:47.750 --> 05:50.830]  The basic standards date back way, way back.
[05:51.250 --> 05:56.030]  There are two wires that are private between your phone and the central office.
[05:57.270 --> 05:58.950]  It's this ingenious interface.
[05:59.150 --> 06:02.730]  Those two wires have lots of different kinds of signals on them.
[06:03.030 --> 06:06.490]  It supplies power back to your telephone, 48 volt DC.
[06:07.050 --> 06:10.690]  There's a current loop on that 48 volt DC when there's a load on it.
[06:10.850 --> 06:16.550]  The central office detects that you've picked up the phone because the circuit closes when you pick up your telephone.
[06:17.010 --> 06:23.330]  During the call or while your phone is off the hook, audio AC signals are superimposed on top of that.
[06:23.910 --> 06:26.650]  While a call is going on, those audio signals are content.
[06:27.250 --> 06:37.410]  But before the call is taken place, while you've gotten a dial tone, those audio signals are signaling to tell the phone company what numbers you're calling if you're using Touch-Tone dialing.
[06:37.910 --> 06:46.210]  So it's this ingenious multiplexed interface that tries to squeeze as many functions out of these two wires as possible.
[06:47.150 --> 06:52.450]  So if you want to tap someone's phone, you have many, many different options.
[06:52.730 --> 06:55.950]  The wiretapper has a huge range of possibilities.
[06:56.430 --> 07:18.710]  So one possibility is to go to the local loop, those two wires, get access to someone, climb their phone pole, go down the manhole, go into their phone closet of their place, or go somewhere near the central office, get access to those two wires, and hook up a tape recorder or a radio transmitter or something like that to it.
[07:19.890 --> 07:25.490]  If the target is using a cordless phone, you might intercept the RF coming out of that cordless phone.
[07:26.370 --> 07:31.490]  Or if they're using a cell phone, you might intercept the radio signals there.
[07:31.770 --> 07:35.130]  You might go to the central office and tap the phone there.
[07:35.670 --> 07:44.070]  If they're making only calls between central offices or long-distance calls, you might tap the inter-office trunks and tap their phone there.
[07:44.310 --> 07:50.910]  You know, there's practically infinite range of possible ways someone who wants to wiretap might do it.
[07:51.150 --> 08:05.350]  We're interested not in all of the possible ways you could wiretap, but very specifically what law enforcement agencies actually choose to do, and what are the possible implications of some of those design choices.
[08:05.990 --> 08:09.430]  So to do that, we wanted to get some wiretap equipment.
[08:09.730 --> 08:25.370]  So it turns out that in the United States, possession of equipment that is primarily useful for the surreptitious interception of wire communications is illegal, and it's one of those really bad felonies to be convicted of.
[08:25.590 --> 08:27.390]  There's a law called 18 U.S.
[08:27.490 --> 08:28.490]  Code 2512.
[08:28.490 --> 08:30.570]  Don't ever get convicted of it.
[08:31.210 --> 08:38.050]  You go to jail for a long time, it's really, really bad to have wiretapping equipment if you're not supposed to have it.
[08:38.690 --> 08:45.770]  And, you know, worse, because of this crime, you can't just call the companies that sell the equipment to law enforcement agencies and buy them.
[08:45.950 --> 08:49.530]  First of all, they're very expensive, and second of all, it's, you know, supposedly illegal.
[08:49.790 --> 08:51.210]  So we had to go to eBay.
[08:59.970 --> 09:08.670]  So, it turns out that law enforcement agencies, when they have extra wiretap equipment, they do the same thing you do when you have an extra stereo.
[09:09.310 --> 09:11.990]  They sell it on eBay.
[09:12.370 --> 09:20.910]  And I spent about a month, I found out the, it turns out, the secret to getting this stuff on eBay is to just find out what the manufacturers of it are and look for them.
[09:21.090 --> 09:24.050]  There are all these little companies and all they sell is wiretap equipment.
[09:24.410 --> 09:28.730]  So, you know, the Ocala, Florida police department, I remember that we got a lot of their stuff.
[09:29.010 --> 09:33.650]  The Chicago police department sold us some digital recorders that still had wiretap recordings on them.
[09:33.650 --> 09:43.930]  I mean, it was just... I filled up my whole lab full of this stuff for a couple thousand dollars worth of expensive wiretapping equipment.
[09:44.070 --> 09:58.610]  Now, I suggest very strongly you don't try this at home because we, it turns out, have... I got this NSF grant from the government to study wiretapping, which turns out to, under 18 U.S.C.
[09:58.790 --> 10:03.630]  2512, exempt us from the, you know, bad felony aspects of this.
[10:03.830 --> 10:12.030]  So, I suggest you don't do this, unless, you know, you've also got an excuse enumerated in that legal section.
[10:12.250 --> 10:16.890]  So, we got a bunch of this surplus wiretap equipment and we played with it.
[10:17.090 --> 10:21.430]  And interestingly, what I'm about to describe, most of what we're...
[10:21.430 --> 10:30.430]  the vulnerabilities that we're going to describe in the talk tonight were discovered in the first hour and a half after opening the first package of equipment that we got.
[10:30.650 --> 10:34.670]  Pretty much all of the first things we thought of turned out to work.
[10:35.050 --> 10:37.850]  We never had to get to testing the second things we thought of.
[10:38.590 --> 10:45.210]  So, I'm going to turn this over to Micah, who's going to talk about some of this, some of this equipment, some of the vulnerabilities we found.
[10:50.340 --> 10:50.740]  Thanks.
[10:52.460 --> 11:00.820]  So, the type of wiretap that we're... that we did most of our work with is the older type, the loop extender wiretaps.
[11:01.140 --> 11:04.620]  And this is really kind of the... what you think of when you think of a conventional wiretap.
[11:04.780 --> 11:11.120]  It's really just putting a pair of wires and actually tapping itself online, cloning that line and sending that to a law enforcement agency.
[11:11.860 --> 11:13.180]  So, there are two parts to it.
[11:13.280 --> 11:15.600]  The first, the loop extender, which I don't know...
[11:16.180 --> 11:17.320]  Actually, we have a picture of this.
[11:17.900 --> 11:19.440]  It's that, which is a felony to own.
[11:21.340 --> 11:29.340]  It's a one-way relay of the subject line, the line that's being targeted, to the law enforcement agency.
[11:29.340 --> 11:41.560]  And at the law enforcement agency, there's a separate box, which is, again, over there, but we'll have pictures of this, which is called a collection or DNR, digital number recorder, which decodes the signals, converts them from analog to digital.
[11:42.000 --> 11:43.780]  It can be hooked up to a laptop, which we have here.
[11:45.080 --> 11:51.180]  And we call the line between the loop extender and the DNR the friendly line, because it's owned by law enforcement, and law enforcement is always friendly.
[11:52.880 --> 12:02.860]  So, loop extender wiretaps are used both for pen register systems, which are just kind of capturing the meta information, what was the telephone number being called, how long did it last, etc.
[12:03.240 --> 12:04.880]  And also for full audio intercepts.
[12:05.380 --> 12:08.640]  For pen register systems, the audio is just muted.
[12:09.860 --> 12:10.960]  So, what does this look like?
[12:11.100 --> 12:14.520]  Looks like this is a loop extender.
[12:14.660 --> 12:16.260]  Looks like something you don't want to bring in an airplane.
[12:16.260 --> 12:27.180]  It has four cables coming out, two for tip and ring, one side of tip and ring going to the subject's line, and the other going to the friendly line.
[12:28.960 --> 12:36.360]  This is the dialed number recorder, which sits at the law enforcement agency, and is the end point of the friendly line.
[12:36.900 --> 12:42.600]  One thing worth pointing out here is that this minimize button is used for full audio intercepts.
[12:42.760 --> 12:53.860]  This is, again, as Matt mentioned, the full audio intercepts are a little bit more expensive, and the reason they're more expensive is because typically wiretaps are only given to one... only set for one person.
[12:54.060 --> 13:02.160]  So, when the subject's spouse, for example, is speaking on the line, an agent has to hit the minimize button so that the spouse's conversation isn't recorded.
[13:05.120 --> 13:11.500]  And this is an example in our lab of what a law enforcement wiretap post looks like.
[13:11.500 --> 13:16.800]  When you have a computer doing the... just kind of as a simple database recording the stuff.
[13:17.540 --> 13:21.880]  The DNR and also a digital tape recorder for the full audio intercepts.
[13:23.460 --> 13:27.520]  So, what we came up with are three novel countermeasures against these loop extender systems.
[13:27.700 --> 13:32.300]  And I'll talk a little bit about CALEA systems later, but for the most part we're going to talk about loop extender systems today.
[13:33.180 --> 13:35.240]  The first is manipulating captured digits.
[13:35.480 --> 13:40.900]  And here we're causing the law enforcement agency to record completely false telephone numbers that were never really dialed.
[13:41.080 --> 13:42.940]  In fact, these telephone numbers may not exist.
[13:43.820 --> 13:45.800]  The second is inserting false call records.
[13:46.000 --> 13:50.220]  Here we can create records of calls that didn't really ever take place.
[13:50.740 --> 13:52.640]  And we just do some kind of neat techniques.
[13:53.260 --> 14:03.660]  And perhaps the most damning is the recording suppression where either the subject of the wiretap or the person he or she is talking to can at will just suppress all of the wiretaps.
[14:06.470 --> 14:14.850]  So, in the first countermeasure, the goal here is to manipulate the captured digit so that the law enforcement agency records incorrect telephone numbers.
[14:15.590 --> 14:22.130]  So, a typical telephone has a set of 12 DTMF signals, 0 through 9 pound and asterisks.
[14:22.650 --> 14:27.010]  And these signals are really just audio signals that are composed of two tones.
[14:27.310 --> 14:31.450]  There's a tone for each column and for each row.
[14:31.450 --> 14:35.930]  And when you dial something, those two corresponding tones are multiplexed on the line.
[14:36.170 --> 14:41.670]  And to the telephone company, you decode the DTMF signals to convert it to its digital manifestation.
[14:42.550 --> 14:49.490]  So, the problem here is that the telephone company's switch does the DTMF decoding.
[14:49.950 --> 14:57.490]  But at the same hand, because this telephone line is essentially cloned, the DNRs also have to do their own DTMF decoding.
[14:57.490 --> 15:04.650]  of getting those sounds that you hear when dialing a number and decoding them into their digital counterparts.
[15:05.350 --> 15:10.230]  So, the goal for the law enforcement is for the DNR box to mimic exactly the actions of the telephone switch.
[15:11.570 --> 15:17.150]  As it turns out, which may be obvious, no two analog devices are exactly the same.
[15:17.150 --> 15:35.390]  So, although there are exact specifications that exist and tolerances for how close the frequencies have to be and the amplitude and twist and so on and so forth, you can always get, because it's an analog device and it's not perfect, you can always get as close to the line between acceptable and not acceptable and you can get arbitrarily close.
[15:36.210 --> 15:46.990]  So, a subject can dial what we call confusion digits by dialing with certain parameters and by parameters, I mean frequency, amplitude, twist, and so forth, that's just outside the switch's range.
[15:47.370 --> 15:54.070]  So, what this means is, yes, you know, you'll hear a tone, but it'll be slightly skewed so that the telephone company switch will completely ignore it.
[15:54.150 --> 15:54.910]  It won't think it's valid.
[15:55.130 --> 15:59.010]  But, on the other hand, the law enforcement will accept it as being perfectly fine.
[15:59.750 --> 16:15.250]  Now, you can do the exact opposite, and we call this evasion digits, where you dial digits that are just within the switch's range, so the switch will view it as legitimate, but with pretty high probability, the tap won't hear it at all.
[16:15.730 --> 16:18.250]  So, if you can do this, then the tap just misses the telephone number entirely.
[16:19.450 --> 16:20.690]  So, how do you do this?
[16:20.770 --> 16:21.770]  How do you know what these ranges are?
[16:21.970 --> 16:30.270]  Well, it turns out, all you really need to do is know what the ranges for the law enforcement wiretap are, excuse me, for the switch.
[16:30.790 --> 16:33.370]  And you don't need to actually probe the law enforcement wiretap.
[16:33.550 --> 16:41.550]  So, you can use a laptop computer by just dialing a telephone number and doing a binary search by just adjusting these parameters and seeing if the call goes through.
[16:42.110 --> 16:46.090]  And to test all parameters and all numbers takes about 120 minutes or so.
[16:46.470 --> 16:50.110]  But keep in mind, you don't have to do this every time you want to do confusion and evasion digits.
[16:50.310 --> 16:53.750]  This is something that you can do once a day before you make your surreptitious calls.
[16:55.590 --> 16:58.130]  So, why are confusion and evasion possible?
[16:58.550 --> 17:01.410]  Well, this is just kind of a graphic representation.
[17:02.290 --> 17:05.470]  So, you have the grey bars indicating what's acceptable.
[17:05.870 --> 17:14.070]  The one on top to the CO, the central office, and to the bottom to the DTMF decoder that's running at the law enforcement agency.
[17:14.790 --> 17:21.190]  And as you can see, because they're analog devices and not perfect and made from commodity parts, they don't line up exactly.
[17:21.670 --> 17:32.170]  So, there's some area where you can dial to the right, for example, which is confusion, because it's not accepted by the central office and it is accepted by the DTMF decoder.
[17:33.030 --> 17:35.370]  And likewise for evasion on the left.
[17:35.610 --> 17:39.010]  And again, you don't know exactly how these things line up, so you have to try on both ends of the spectrum.
[17:41.010 --> 17:47.430]  So, in our second countermeasure, we insert false call records that never actually have taken place.
[17:48.550 --> 17:56.650]  So, keep in mind that loop extenders relay call audio exactly as how it is and then send it from the target line to the friendly line completely unchanged.
[17:56.650 --> 18:04.470]  Now, the friendly line between the loop extender and the DNR, the law enforcement agency, is just a standard telephone line.
[18:04.610 --> 18:05.750]  There's nothing really special about it.
[18:05.950 --> 18:13.270]  So, you can't relay this DC line status through the friendly line or you're going to disconnect the friendly line.
[18:13.490 --> 18:22.130]  So, the way that law enforcement agencies do this or the manufacturers of these devices do this is they use in-band signaling, which is always a good idea.
[18:23.830 --> 18:31.070]  And the way they do in-band signaling is they have the loop extender generate an idle tone which corresponds to the DTMF C tone.
[18:31.670 --> 18:36.170]  Now, a standard telephone has 12 DTMF tones, but there are actually 16 described in the spec.
[18:36.870 --> 18:38.210]  And these aren't anything special.
[18:38.350 --> 18:38.830]  They're not magical.
[18:39.010 --> 18:39.890]  They're just different tones.
[18:41.010 --> 18:44.690]  So, the C tone is played whenever the subject goes off-hook.
[18:45.910 --> 18:46.350]  So...
[18:46.350 --> 18:46.990]  On-hook.
[18:47.190 --> 18:47.630]  Sorry.
[18:47.890 --> 18:48.550]  It's on-hook.
[18:48.670 --> 18:48.830]  Thank you.
[18:49.330 --> 19:01.390]  And when you pick up the phone, the C tone turns off so that by having the C tone, the law enforcement agency knows when to record and when the phone isn't being used.
[19:04.560 --> 19:06.700]  Well, the C tone isn't anything magical.
[19:06.920 --> 19:10.060]  It's just a standard telephone tone.
[19:10.340 --> 19:19.760]  And as any of you know, when you're talking on the phone and someone picks up another phone in your house and starts dialing because they didn't see if anybody was on the line first, which is very annoying, you can hear this phone.
[19:19.900 --> 19:26.400]  So, there's nothing special about dialing DTMF tones after the call has been established.
[19:27.060 --> 19:37.820]  So, the problem from the law enforcement perspective is the DNR can't distinguish the authentic C tones that are generated by the loop extender from a fake C tone sent by the subject of the actual line.
[19:37.980 --> 19:41.840]  So, as long as you're capable of generating a C tone, you can screw with the DNR.
[19:42.640 --> 19:51.000]  So, in both cases, the DNR detects that the target line has been hung up, regardless of whether the target line has indeed been hung up.
[19:51.900 --> 20:04.840]  So, by pressing a C tone, and again, this can be done either by the subject of the wiretap or the person he or she is talking to, the recording equipment just shuts off, says, okay, thank you very much for ending your call, and logs the end of a next call.
[20:04.840 --> 20:10.580]  And then when that happens, then when you stop pressing the C tone, the recording resumes.
[20:11.540 --> 20:30.000]  So, all you need to do is basically to insert fake call records is to dial a number, generate a talk on the phone, generate a C tone for a few seconds, let go of the C tone, and then dial another number, and the law enforcement agency will record that second number as the one with the audio.
[20:33.160 --> 20:36.660]  The third countermeasure is to disable audio recording entirely.
[20:37.360 --> 20:44.340]  And, as I mentioned before, nothing gets recorded when the C tone is being pressed because the law enforcement agency thinks the phone isn't being used.
[20:45.360 --> 20:50.900]  So, if you just hold down a C tone, you get the law enforcement agency to just stop recording entirely.
[20:51.300 --> 20:54.420]  But the problem with this is that the C tone is too loud to talk over.
[20:54.420 --> 20:58.560]  But, as it turns out, you don't really need to play the C tone at full volume.
[20:58.920 --> 21:01.440]  All you need to do is play it at one one-thousandth of its normal volume.
[21:01.860 --> 21:05.860]  And the law enforcement equipment just kind of stops.
[21:06.740 --> 21:08.600]  So, this sounds like a mmmm.
[21:08.680 --> 21:10.140]  I've never done with this before.
[21:10.280 --> 21:10.500]  You'll hear it.
[21:10.620 --> 21:11.160]  Yeah, you'll hear it.
[21:11.580 --> 21:11.900]  Yeah.
[21:12.000 --> 21:13.560]  I want to blow out the speaker system now.
[21:14.880 --> 21:16.840]  It also shuts off the speakers here.
[21:17.020 --> 21:17.180]  Yeah.
[21:19.240 --> 21:20.660]  It's fine talking over this.
[21:20.900 --> 21:22.640]  I do it all the time now with all my friends.
[21:22.640 --> 21:24.980]  And it's fine.
[21:25.400 --> 21:26.400]  And I haven't been arrested yet.
[21:27.520 --> 21:31.440]  So, and again, this can be done either by the subject of the wiretap or the other party.
[21:31.540 --> 21:35.180]  It doesn't matter who's generating the tone because as long as the tone is generated over the line.
[21:36.900 --> 21:38.760]  So, there might be some similarities here.
[21:39.120 --> 21:40.200]  Actually, there are some similarities.
[21:40.460 --> 22:00.340]  In the 1960s, as was kind of demonstrated or talked about in the last session here, there was this vulnerability with the long-distance carriers that occurred when, you know, you could dial a 2600 hertz tone and you could use... you could exploit a race condition and make free long-distance telephone calls.
[22:00.960 --> 22:07.700]  Well, 30 years later in the 1990s, technology has become much more complex and now we have two tones that we have to deal with.
[22:09.120 --> 22:16.320]  So, if you are capable of producing two tones, then you can stop audio recording and sort fake call records and do a bunch of other mischievous things.
[22:16.940 --> 22:24.400]  And, you know, either with $20 worth of radio jack parts or with a slide whistle or with a laptop computer, this is pretty easy to do.
[22:27.440 --> 22:29.140]  So, previously I have been talking...
[22:29.140 --> 22:29.800]  Oh, crap.
[22:30.620 --> 22:31.620]  How do I...
[22:31.620 --> 22:32.720]  I have no idea.
[22:34.040 --> 22:34.480]  What?
[22:34.680 --> 22:35.020]  It's good.
[22:35.860 --> 22:40.040]  We did, by the way, try and make some C tone whistles that we could give away to you guys.
[22:40.260 --> 22:42.760]  But the closest I could get would be C tone pan pipes.
[22:44.780 --> 22:45.820]  It does work, though.
[22:45.940 --> 22:48.260]  You can take little pipes about...
[22:48.260 --> 22:48.920]  What?
[22:49.260 --> 22:53.880]  The 852 is about this big and the 1633 is about this big and hold them together and blow in them and you get a C tone out.
[22:56.880 --> 23:01.820]  So, previously I was describing vulnerabilities with the old loop extender systems.
[23:02.160 --> 23:11.860]  But as Matt mentioned in 94, Clinton signed the Communications Assistance for Law Enforcement Act, CALEA, which mandated a standard between the law enforcement agencies and the telephone companies.
[23:12.140 --> 23:16.780]  And why this was needed was because traditional landlines weren't necessarily always the case.
[23:17.120 --> 23:29.980]  Now you have cell phones and voice over IP and there was really a need from the law enforcement or Department of Justice perspective of getting a way to standardize how wiretaps were doing so that law enforcement agency didn't have to have 20 different systems.
[23:31.220 --> 23:37.960]  So, with CALEA system, there was no kind of loop extender system or difference there.
[23:37.960 --> 23:38.980]  This really just...
[23:38.980 --> 23:43.200]  The data is gathered directly from the telephone switch and related to the law enforcement agency.
[23:43.680 --> 23:44.220]  And no...
[23:44.220 --> 23:48.940]  They didn't use in-band signaling any longer because they separated data into two separate channels.
[23:49.140 --> 23:54.380]  The call data channel which carried the meta information such as signaling data, call times, numbers, dialed, et cetera.
[23:54.640 --> 23:58.580]  And also a separate call content channel which just carried the live audio.
[23:58.820 --> 24:06.560]  And you can go to the J standard, the NCJ standard and look up what the packet formats are of the CDC and it looks very much like an RFC.
[24:08.300 --> 24:13.520]  So, one question is, are CALEA systems trustworthy then because they don't have this in-band signaling?
[24:14.140 --> 24:16.760]  And on first approximation, the answer may be yes, they are.
[24:16.960 --> 24:23.360]  But as it turns out, the Department of Justice specifically requested that they have C tones on CALEA call content channels.
[24:25.480 --> 24:28.460]  So, again, these...
[24:28.460 --> 24:34.120]  What the Department of Justice asked for was a way that if there was a C tone, the recording would just stop.
[24:34.860 --> 24:36.760]  Just as it was with loop extenders.
[24:38.060 --> 24:42.280]  And the FCC said, no, you know, you can't have that as a requirement.
[24:42.680 --> 24:46.780]  But the vendors who are the ones selling the equipment wanted to make the Department of Justice happy.
[24:47.040 --> 24:50.820]  So, in many cases, the C tone functionality does exist.
[24:52.580 --> 24:54.080]  So, what are the implications here?
[24:54.500 --> 24:58.020]  Well, in some systems, you can disrupt interception.
[24:58.800 --> 25:01.140]  And here, you know, you just cause the interception to fail.
[25:01.260 --> 25:03.480]  And this is with the C tone recording suppression.
[25:03.740 --> 25:08.040]  But perhaps even worse, particularly from the illegal standpoint, you can mislead interceptors.
[25:08.540 --> 25:11.440]  So, you can insert... you can spoof calls.
[25:11.500 --> 25:12.340]  I can frame someone.
[25:12.500 --> 25:17.560]  I can add DTMF confusion and evasion to obscure and mask my telephone numbers.
[25:17.560 --> 25:28.980]  And also, something we didn't talk about today, but if you look at www.crypto.com and look at our paper, we also are able to spoof incoming caller ID kind of using the same in-band signaling vulnerabilities.
[25:30.120 --> 25:38.400]  So, at this point, I'm going to hand it off to Eric and Sandy, who are going to run through a demo of our system.
[25:55.430 --> 25:55.790]  Okay.
[25:55.990 --> 25:56.350]  Okay.
[25:56.350 --> 25:59.730]  So, the first thing that we'd like to show you is what the law enforcement sees.
[26:00.610 --> 26:01.350]  Ah, sorry.
[26:05.630 --> 26:11.370]  The first thing we'd like to show you is what the law enforcement sees when someone that have a wiretap line is making a normal call.
[26:12.330 --> 26:16.510]  So, this is the display at police headquarters.
[26:16.770 --> 26:20.070]  So, we've hooked it up to our law enforcement laptop here.
[26:20.230 --> 26:30.850]  So, this is what the guy with the worst job in law enforcement of sitting there listening to the recorder sees on the laptop screen while not looking at the net or whatever.
[26:33.090 --> 26:40.650]  And just to clarify a little, the payphone here is just a prop because always you're talking to some shady person on a street corner at a payphone.
[26:41.590 --> 26:45.810]  It has nothing at all to do with the actual technical aspects of this.
[26:46.210 --> 26:46.530]  So...
[26:46.950 --> 26:47.810]  Could be any old phone.
[26:47.810 --> 26:47.910]  Yeah.
[26:47.990 --> 26:48.690]  In a minute, I'll show you...
[26:48.690 --> 26:49.450]  We like phones.
[26:49.570 --> 26:49.730]  Yeah.
[26:49.930 --> 26:56.530]  I'll show you with this phone because this has the magical fourth column, which your standard run-of-the-mill phone doesn't have.
[26:56.750 --> 26:56.850]  Right.
[26:57.290 --> 26:58.690]  So, I should just explain this display.
[26:58.850 --> 27:01.430]  See, on the bottom is the log of all of the past calls.
[27:01.590 --> 27:02.930]  This is just while we were setting it up.
[27:03.730 --> 27:11.590]  It's just got, in the upper left corner there, you'll see this little kind of grayed-out display showing the line that this is currently looking at.
[27:11.710 --> 27:12.470]  This has been configured.
[27:12.550 --> 27:14.570]  That's a notation of the phone number of the target.
[27:14.730 --> 27:17.810]  In this case, 555-555-1003.
[27:18.050 --> 27:19.690]  It's currently on hook.
[27:20.430 --> 27:23.550]  And it's owned by subject Tony Soprano.
[27:24.930 --> 27:25.450]  But...
[27:25.450 --> 27:25.990]  This is...
[27:25.990 --> 27:27.430]  By the way, this is not real data.
[27:27.570 --> 27:28.670]  This is data we made up.
[27:29.770 --> 27:30.290]  But...
[27:30.290 --> 27:31.150]  The...
[27:31.150 --> 27:34.690]  And we'll see that if Tony over here...
[27:34.690 --> 27:35.110]  Alice.
[27:35.770 --> 27:36.210]  Uh...
[27:36.210 --> 27:36.970]  Or Alice.
[27:37.310 --> 27:37.950]  Picks up the phone.
[27:38.170 --> 27:38.650]  The line...
[27:38.650 --> 27:43.470]  If you look in the upper left corner, the line status will change to go off hook.
[27:43.690 --> 27:43.930]  Okay.
[27:43.930 --> 27:45.510]  And it indicates that it's recording.
[27:45.810 --> 27:48.630]  Now they know I'm about to make a call to my friend, Bob Corleone.
[27:51.900 --> 27:55.040]  We should be getting audio out through the laptop interface as well.
[27:57.760 --> 27:58.200]  Hello?
[27:58.540 --> 27:58.840]  Hi.
[27:59.000 --> 27:59.140]  Bob?
[27:59.420 --> 27:59.640]  Yeah.
[28:00.080 --> 28:01.340]  Oh, it's Alice.
[28:01.760 --> 28:02.820]  You know...
[28:03.480 --> 28:06.240]  I'd love to discuss a crime with you, but somebody might be listening.
[28:06.760 --> 28:09.420]  Now, one thing about this is that if they don't...
[28:09.420 --> 28:16.000]  If they do have a Title III wiretap warrant, that they're allowed to listen to the content, they can't listen to the content legally.
[28:16.000 --> 28:16.380]  Yeah.
[28:16.740 --> 28:17.120]  If...
[28:17.120 --> 28:18.400]  You seem to be talking into the phone.
[28:18.500 --> 28:18.680]  Sorry.
[28:19.400 --> 28:26.640]  Well, they can't listen to the content legally if somebody who is not mentioned in the warrant gets on the phone.
[28:26.640 --> 28:29.760]  So if I'm to hand the phone to you, and you talk to Bob...
[28:30.320 --> 28:35.720]  So I, with this law enforcement job, I have to push the little red minimize button.
[28:36.320 --> 28:36.840]  So say hi to Bob.
[28:36.880 --> 28:40.680]  And you'll see, if you look in that upper left corner, now it says min.
[28:40.860 --> 28:43.060]  And that means I've pushed the little minimize button.
[28:43.200 --> 28:46.340]  It has turned off the recording, and we're no longer recording the call.
[28:46.560 --> 28:49.440]  But he still has to listen, because he's got to know when I get back on the line.
[28:49.760 --> 28:49.880]  Yeah.
[28:50.020 --> 28:55.000]  Now, unfortunately, we can't really tell with these microphones here when the audio is on and when it's off.
[28:55.000 --> 28:57.820]  Is there any way to turn off the desk mics for the...
[28:57.820 --> 28:59.800]  Next one, just leave the laptop audio on.
[29:01.200 --> 29:01.640]  Okay.
[29:01.920 --> 29:02.000]  Great.
[29:02.300 --> 29:03.760]  Do we have audio?
[29:04.520 --> 29:05.320]  One, two, three.
[29:05.440 --> 29:05.860]  Can you hear me?
[29:06.160 --> 29:06.880]  Am I coming through?
[29:07.100 --> 29:07.360]  Hello?
[29:07.860 --> 29:08.280]  Let's see.
[29:08.920 --> 29:09.040]  Yeah.
[29:09.380 --> 29:10.260]  Am I coming through?
[29:10.660 --> 29:10.860]  Hello?
[29:11.300 --> 29:14.120]  Do you have any audio?
[29:14.460 --> 29:14.760]  No.
[29:15.160 --> 29:15.300]  No.
[29:22.150 --> 29:22.590]  Okay.
[29:22.710 --> 29:22.930]  Hello?
[29:23.110 --> 29:23.950]  Now you got me.
[29:24.290 --> 29:24.490]  Okay.
[29:25.090 --> 29:25.170]  Good.
[29:34.110 --> 29:35.870]  Is this a mechanical problem?
[29:35.870 --> 29:36.510]  I don't know.
[29:36.610 --> 29:37.370]  It's a serial plug.
[29:38.150 --> 29:38.610]  Soldering!
[29:40.090 --> 29:41.810]  We do have a soldering iron with us.
[29:42.070 --> 29:42.130]  No.
[29:43.850 --> 29:44.570]  Are you on?
[29:44.810 --> 29:45.350]  I'm on.
[29:45.450 --> 29:45.830]  Can you hear me?
[29:46.530 --> 29:46.730]  No.
[29:58.110 --> 29:59.350]  Please continue talking.
[29:59.590 --> 30:00.490]  You can't tell.
[30:00.870 --> 30:00.990]  Okay.
[30:01.270 --> 30:01.470]  Go.
[30:03.670 --> 30:06.770]  So this is a sort of modern day equivalent of a blue box.
[30:07.530 --> 30:07.890]  Wait.
[30:08.150 --> 30:09.190]  Let's just do it this way.
[30:09.390 --> 30:10.050]  Can we turn it on?
[30:10.350 --> 30:11.990]  Is there any way to turn just this one?
[30:12.390 --> 30:12.550]  No.
[30:12.830 --> 30:13.190]  There isn't.
[30:31.120 --> 30:31.480]  Yeah.
[30:31.520 --> 30:32.580]  Can we just have the desk please?
[30:32.900 --> 30:33.220]  Thanks.
[30:35.200 --> 30:35.620]  All right.
[30:35.680 --> 30:36.220]  Does that work better?
[30:36.480 --> 30:37.100]  Now can you hear me?
[30:37.140 --> 30:37.380]  Yes.
[30:37.380 --> 30:37.600]  All right.
[30:37.600 --> 30:37.920]  Okay.
[30:38.020 --> 30:38.100]  Great.
[30:38.100 --> 30:38.540]  Yeah.
[30:38.780 --> 30:40.680]  This is the modern day equivalent of a blue box.
[30:42.880 --> 30:44.600]  It's going to have feedback if it's much louder.
[30:45.880 --> 30:49.100]  If I want to turn off the recording, I can press...
[30:49.720 --> 30:50.400]  Can you hear it?
[30:50.560 --> 30:52.440]  I can press the C tone button here.
[30:53.380 --> 30:54.020]  Can you hear that?
[30:54.200 --> 30:56.320]  But I'm going to choose to do it from my laptop instead.
[30:59.200 --> 31:04.500]  Now if you notice, as far as the phone, as far as the law enforcement agency is concerned, I have one.
[31:04.720 --> 31:04.940]  Wait.
[31:06.480 --> 31:06.780]  Yeah.
[31:07.120 --> 31:08.980]  This arm is just not going to work.
[31:10.500 --> 31:10.940]  Yeah.
[31:11.080 --> 31:16.760]  Basically, as far as the law enforcement agency is concerned, because the C tone is playing, it hung up the telephone.
[31:17.140 --> 31:21.620]  But they're still talking to each other on the...
[31:21.620 --> 31:21.900]  Yeah.
[31:22.320 --> 31:25.520]  Can you pick up your stop plane C tone?
[31:31.020 --> 31:32.080]  It's not recording still.
[31:33.220 --> 31:33.620]  Yeah.
[31:33.620 --> 31:35.500]  It's just a damn sure out there.
[31:37.420 --> 31:38.140]  I don't know.
[31:39.420 --> 31:39.820]  Yeah.
[31:40.700 --> 31:41.540]  So pick up the phone.
[31:41.660 --> 31:43.540]  Okay, now it's lost extension to loop extender.
[31:44.600 --> 31:45.020]  Okay, now...
[31:45.020 --> 31:45.260]  Oh, yeah.
[31:45.420 --> 31:45.540]  Oh, yeah.
[31:45.540 --> 31:45.780]  Okay, here we go.
[31:46.320 --> 31:46.460]  Yeah.
[31:47.900 --> 31:49.200]  Can people see this red light?
[31:49.900 --> 31:51.780]  Can people see the tiny red light here?
[31:53.820 --> 31:54.220]  Yeah.
[31:54.380 --> 31:56.140]  Yeah, so that red light...
[31:56.920 --> 31:58.020]  Oh, the mic's not that.
[32:00.840 --> 32:07.220]  The red light here is an indicator that the tape recorder back here is actually recording.
[32:07.460 --> 32:12.820]  So, for example, if Sandy picks up the phone again, you see that... well, it's not gone off hook.
[32:12.880 --> 32:14.660]  Now it's gone off hook, so the red light should be on.
[32:14.920 --> 32:17.600]  And if I press the minimize button, it goes off.
[32:18.800 --> 32:19.520]  It blinks.
[32:19.660 --> 32:22.700]  And if I press it again, it's listening again.
[32:22.880 --> 32:31.000]  And if I... like briefly before feedback kicks in, you can hear that the tape recorder is actually recording and playing it.
[32:32.120 --> 32:37.300]  So now just take our word that when the red light is on, the police are recording.
[32:37.480 --> 32:39.000]  And when the red light is off, they aren't.
[32:39.800 --> 32:40.960]  We'll do demos of this.
[32:41.120 --> 32:43.440]  We'll set up downstairs later and do demos of this.
[32:43.940 --> 32:45.960]  Why don't we show the...
[32:46.400 --> 32:46.760]  Yeah.
[32:48.500 --> 32:49.140]  Do I have a microphone?
[32:49.980 --> 32:51.600]  If you plug that thing in.
[32:54.120 --> 32:59.300]  Okay, so the next thing we'd like to show you is how you can make the law enforcement agency think you're dialing any number or...
[32:59.300 --> 33:02.200]  Why don't you dial them in the regular way just to show the dialing?
[33:02.460 --> 33:05.740]  And then, you know, just use the phone and show the dialing first just to...
[33:05.740 --> 33:07.940]  You'll see the digits being dialed as...
[33:15.590 --> 33:15.950]  Right.
[33:16.110 --> 33:16.390]  Okay.
[33:18.230 --> 33:20.750]  So what we want to do is confuse the hell out of them.
[33:21.250 --> 33:23.930]  So we're not going to send just the standard 10 digits.
[33:24.130 --> 33:25.230]  We're going to send 40.
[33:27.410 --> 33:30.430]  Some of them are going to be right and some of them are going to be wrong.
[33:30.430 --> 33:30.710]  Right.
[33:30.810 --> 33:36.550]  Using a combination of confusion and evasion, we probed the central office earlier while you weren't...
[33:36.550 --> 33:36.870]  Looking.
[33:37.050 --> 33:37.210]  Looking.
[33:37.530 --> 33:47.670]  And found out the parameters of the central office to find the confusion and evasion parameters for this particular device for our local phone company.
[33:48.130 --> 33:48.470]  Okay.
[33:48.810 --> 33:51.530]  So if you look in the upper right corner...
[33:51.530 --> 33:52.410]  And you listen.
[33:53.570 --> 33:55.470]  There you go.
[33:55.550 --> 33:56.550]  You're not seizing.
[33:57.510 --> 33:58.010]  Should be.
[33:58.030 --> 33:59.230]  Do you have the line hooked up to that?
[34:00.330 --> 34:00.630]  Yep.
[34:00.790 --> 34:01.010]  Should be.
[34:01.090 --> 34:01.690]  The fumble.
[34:04.050 --> 34:04.810]  Just took a while.
[34:05.510 --> 34:06.090]  Didn't seize.
[34:06.430 --> 34:06.990]  Kill it again.
[34:07.210 --> 34:07.690]  Didn't do it again.
[34:08.030 --> 34:08.610]  First attempt.
[34:09.230 --> 34:09.350]  Yeah.
[34:09.890 --> 34:10.130]  Yeah.
[34:10.190 --> 34:10.770]  That one didn't count.
[34:12.850 --> 34:13.250]  Ready?
[34:13.510 --> 34:13.630]  Yep.
[34:16.880 --> 34:17.480]  Why isn't it?
[34:21.740 --> 34:22.140]  Yeah.
[34:23.680 --> 34:24.400]  So the...
[34:24.400 --> 34:24.540]  Okay.
[34:24.620 --> 34:24.820]  All right.
[34:24.880 --> 34:25.700]  As you can tell, it is...
[34:25.700 --> 34:26.440]  It is confused.
[34:29.100 --> 34:29.620]  All right.
[34:30.200 --> 34:31.540]  You want to try changing cables?
[34:31.580 --> 34:31.720]  Are your levels correct?
[34:32.340 --> 34:33.140]  They may not be.
[34:33.300 --> 34:33.540]  Let me see.
[34:38.930 --> 34:39.290]  Yeah.
[34:39.850 --> 34:39.990]  All right.
[34:40.050 --> 34:40.370]  Try again.
[34:43.090 --> 34:47.350]  So the number we're actually dialing is 987-654-3210.
[34:48.550 --> 34:48.910]  No.
[34:49.750 --> 34:50.110]  And...
[34:50.970 --> 34:52.370]  Why is it getting the phone split up?
[34:52.550 --> 34:53.210]  I have no idea.
[34:53.650 --> 34:55.350]  Let me make sure that the phone is...
[34:55.350 --> 34:55.370]  Yeah.
[34:55.430 --> 34:56.090]  We're doing practice.
[34:56.550 --> 34:57.070]  Hold on one second.
[34:57.470 --> 34:57.650]  Yeah.
[34:58.090 --> 34:58.370]  Sorry.
[34:58.490 --> 34:58.630]  Good.
[34:58.850 --> 34:59.090]  I have no idea.
[34:59.950 --> 35:00.910]  It's because...
[35:00.910 --> 35:01.170]  Hit your...
[35:02.130 --> 35:03.110]  This is right here.
[35:03.870 --> 35:05.110]  Get rid of the Play C thing.
[35:05.530 --> 35:05.970]  Got it.
[35:08.330 --> 35:08.810]  Okay.
[35:09.630 --> 35:10.430]  Should be all set.
[35:11.510 --> 35:12.450]  No, you should be fine.
[35:12.650 --> 35:12.810]  Yeah.
[35:13.190 --> 35:13.470]  All right.
[35:39.060 --> 35:39.540]  So...
[35:44.710 --> 35:46.690]  Basically, what you've seen is that...
[35:46.690 --> 35:55.930]  What you've seen is that we've successfully gotten it to make a phone call to a number that we chose by probing only the central office.
[35:56.210 --> 36:04.670]  And it thinks we called 373-501-1220 when, in fact, we called 1-987-654-3210.
[36:05.590 --> 36:19.570]  Earlier, what you saw was we were managing to remotely turn off the law enforcement recorder just by playing this low-level C tone on the line at 40 dB below its normal level, thanks to the magic of automatic gain control that went through just fine.
[36:19.570 --> 36:24.750]  And we can also insert fake records in here of calls that never took place.
[36:25.230 --> 36:31.230]  A lot of these bugs have been carried over into the CALEA systems because they're backward compatible and hence bug compatible.
[36:31.590 --> 36:32.070]  Any questions?
[36:32.570 --> 36:33.010]  No.
[36:33.310 --> 36:33.490]  All right.
[36:33.930 --> 36:37.630]  Please use the microphones and state your name and social security number.
[36:38.510 --> 36:40.370]  We need to do the caller ID for you.
[36:40.630 --> 36:40.890]  Yeah.
[36:41.150 --> 36:42.630]  We're out of time, so...
[36:42.630 --> 36:43.070]  All right.
[36:43.390 --> 36:43.770]  Caller ID.
[36:45.350 --> 36:45.870]  Yeah.
[36:46.750 --> 36:53.470]  When you used the C tone to stop the recording and then stopped playing the C tone, why did the recording not resume?
[36:53.990 --> 36:55.970]  Well, because it now thinks it's...
[36:56.670 --> 36:58.290]  We didn't stop playing the C tone.
[36:58.410 --> 36:59.850]  You stopped hearing the C tone.
[36:59.990 --> 37:00.110]  Got it.
[37:00.190 --> 37:02.550]  Because it causes the tape recorder to turn off.
[37:02.710 --> 37:04.530]  And I was playing through the tape recorder interface.
[37:04.850 --> 37:05.170]  Okay.
[37:05.290 --> 37:07.710]  And my other question is, is it 30 dB or 40 dB?
[37:07.870 --> 37:09.830]  Because 40 dB is a 10,000th, not a 1,000th.
[37:09.870 --> 37:09.970]  Right.
[37:09.970 --> 37:14.990]  So it's minus 40 dBm and the normal level is minus 10 dBm.
[37:15.110 --> 37:15.530]  Got it.
[37:16.090 --> 37:16.570]  So...
[37:16.570 --> 37:19.870]  How do you check the limits of the equipment, the upper and the lower?
[37:20.150 --> 37:20.450]  Sorry?
[37:20.650 --> 37:22.710]  How do you check the tolerances?
[37:23.190 --> 37:25.990]  So what we do is you ask the central office.
[37:26.190 --> 37:34.810]  The central office will happily tell you whether your digit is compatible with its DTMF decoder by either placing or not placing a call dialed with it.
[37:34.970 --> 37:43.090]  So we basically binary search on all of the parameters for all of the digits and find them for the amplitude, the frequencies on the upper end and the lower end.
[37:43.550 --> 37:44.810]  It takes about an hour or so.
[37:44.970 --> 37:46.750]  We dialed a friend's house a lot of times.
[37:47.070 --> 37:47.370]  Yeah.
[37:52.590 --> 37:55.390]  How do you know when you're not triggering the...
[37:55.390 --> 37:56.430]  Oh, we don't.
[37:56.850 --> 37:58.990]  That's why we're dialing 40 of these digits.
[37:59.530 --> 38:06.490]  Probabilistically, we know it's going to not accept some of the real ones and accept some extraneous ones that the central office isn't.
[38:06.670 --> 38:10.590]  So we're just relying on the fact that we don't know how it's different, but we know that it is different.
[38:12.130 --> 38:15.370]  Unless the tappy is fully paranoid, how do you know if you're being tapped?
[38:16.170 --> 38:22.230]  Well, the nice thing about this is since you can still make and receive calls in the normal way, you don't have to know whether you're being tapped.
[38:22.230 --> 38:22.850]  That you consider normal.
[38:25.310 --> 38:28.930]  More seriously, how tappable is voice over IP realistically?
[38:28.930 --> 38:29.330]  Honestly.
[38:29.990 --> 38:33.190]  Well, I mean, this is a totally different kettle of fish.
[38:33.770 --> 38:36.710]  You know, voice over IP can be tapped in a number of different ways.
[38:36.870 --> 38:45.410]  And because this is a newer technology, the tapping technology for doing it is just being developed now.
[38:45.630 --> 38:49.170]  So in some sense, it's probably less compatible with the old bugs.
[38:49.170 --> 38:52.130]  But of course, it's more complicated, so there are new bugs.
[38:52.130 --> 38:58.570]  So, you know, whether or not analogous vulnerabilities like this exist, almost certainly.
[38:58.770 --> 39:02.370]  Whether or not these particular vulnerabilities exist, who knows?
[39:02.670 --> 39:09.990]  Since you don't know, since presumably law enforcement doesn't know where the caller is using the voice over IP box, it would seem really, really tough to do.
[39:10.230 --> 39:12.950]  Do you have any real knowledge of how realistic it is?
[39:12.950 --> 39:14.230]  To find out what kind of service...
[39:14.230 --> 39:18.070]  Yeah, they tend to find out something about their targets first.
[39:18.510 --> 39:22.430]  They have to know who's their phone provider, and they can find out that sort of stuff.
[39:22.470 --> 39:26.090]  So is there a CO kind of concept in voice over IP?
[39:26.410 --> 39:30.310]  Well, there are service providers, and they can be served with wiretap orders.
[39:30.390 --> 39:35.770]  So does all the traffic... so do we presume all the traffic on these voice over IP calls go through their routers?
[39:35.770 --> 39:36.170]  It depends.
[39:36.370 --> 39:44.950]  I mean, you know, some of the... some VoIP systems do peer-to-peer content routing, but there's still some records being made at the local central office.
[39:45.090 --> 39:45.350]  Thanks.
[39:45.910 --> 39:46.470]  Sorry.
[39:47.630 --> 39:49.750]  I'm not sure how many seconds do we have left?
[39:49.890 --> 39:50.110]  Ten minutes.
[39:50.330 --> 39:50.450]  Okay.
[39:50.730 --> 39:52.250]  All right.
[39:53.330 --> 39:55.110]  Just a clarification.
[39:55.570 --> 40:04.090]  Regarding the evasion slash infusion of digits, since you can't know how...
[40:04.090 --> 40:09.650]  Like, you know the spectrum for the DTMF, but you don't know it for the DNR.
[40:10.010 --> 40:16.010]  So how do you know whether you're evading digits or putting extra digits?
[40:16.050 --> 40:17.030]  Or do you not know?
[40:17.210 --> 40:17.730]  We don't.
[40:19.650 --> 40:20.630]  Yeah, we don't know.
[40:20.750 --> 40:32.710]  We just rely... we just send enough digits, enough of the confusion digits, that we probabilistically know that what the law enforcement agency gets is this completely different picture than the central office gets.
[40:32.710 --> 40:36.670]  We can't control precisely what picture the law enforcement agency is getting.
[40:36.890 --> 40:45.050]  We can just be probabilistically confident that they're getting something that's not at all close to reality.
[40:45.270 --> 40:46.050]  Actually, if I could...
[40:46.050 --> 40:46.510]  Yeah.
[40:46.510 --> 40:46.810]  Is this on?
[40:47.250 --> 40:47.550]  Yeah.
[40:48.550 --> 40:50.070]  If I could just add to that a little bit.
[40:50.730 --> 40:57.970]  With confusion and evasion, you always know whether you're trying to do confusion or evasion, because you've probed the local switch.
[40:58.110 --> 41:02.330]  What you don't really know is when you do confusion whether or not it will be acceptable or not.
[41:02.850 --> 41:04.410]  And same with evasion.
[41:04.970 --> 41:13.090]  So, you know, by dialing 40 digits, the probabilities are in your favor of screwing up the law enforcement agency machine.
[41:14.070 --> 41:21.370]  And what we're looking for is just enough that them trying an exhaustive search of all the numbers that they got would not give them a number.
[41:21.610 --> 41:23.250]  Because they're going to miss some of the numbers.
[41:24.610 --> 41:29.130]  So even if they found most of them, they're still missing a few.
[41:29.890 --> 41:32.230]  Or they might just miss all of them.
[41:32.230 --> 41:40.850]  But for them to have to go through all of the numbers and punch all of those phone numbers and try and recreate the call, it's next impossible.
[41:46.020 --> 41:50.660]  To actually know whether or not you're confusing or evading, would you not also have to probe the DNR equipment?
[41:50.940 --> 41:53.260]  No, we don't get to probe the DNR equipment.
[41:53.480 --> 41:53.620]  Right.
[41:53.860 --> 41:55.760]  We only get to probe our central office.
[41:56.020 --> 41:56.240]  Right.
[41:56.280 --> 41:58.920]  But what happens if the tolerances are slightly to the other side?
[41:58.920 --> 42:05.020]  So you know exactly what your local central office will accept.
[42:05.180 --> 42:05.380]  Right.
[42:05.480 --> 42:09.060]  But how do you know to which side the DNR tolerance is?
[42:09.320 --> 42:16.160]  So if you make something slightly more towards the spec, then that is possibly evasion.
[42:16.300 --> 42:22.720]  Because you know that your central office is at this point and it's going to see that number.
[42:23.060 --> 42:28.520]  But the DNR may be closer to the spec than your central office is.
[42:28.520 --> 42:38.620]  The same way with confusion, you make it slightly more than what your central office will accept.
[42:40.900 --> 42:51.960]  So basically, when you're trying to do evasion dialing, with high but not 100% probability, the central office will accept it but the law enforcement agency won't.
[42:52.040 --> 42:52.520]  You don't know.
[42:52.720 --> 42:53.100]  Right.
[42:53.100 --> 42:54.120]  But it may or may not.
[42:54.240 --> 43:03.680]  With confusion dialing, with high but not 100% probability, the law enforcement agency will accept it but you know because you've probed the central office won't.
[43:03.840 --> 43:04.080]  Right.
[43:04.080 --> 43:17.620]  So just by mixing your, dialing the real digits using the confusion technique and throwing in a bunch of fake evasion digits between them, what the law enforcement agency gets is this totally random looking picture in the aggregate.
[43:17.620 --> 43:17.920]  Yeah.
[43:18.080 --> 43:20.140]  But for any given digit, you don't know what's going to happen.
[43:20.360 --> 43:24.340]  Well, the confusion digits though should show up on the DNR but not at the telco, right?
[43:24.480 --> 43:28.160]  So it should be possible to actually send an innocuous number that looks real.
[43:28.560 --> 43:29.000]  That's right.
[43:29.140 --> 43:29.820]  And then dial a separate number.
[43:29.940 --> 43:30.040]  Yes.
[43:30.040 --> 43:30.280]  Okay.
[43:30.740 --> 43:31.240]  Just checking.
[43:32.260 --> 43:36.280]  Is the process for tapping cell phones at all similar or is that...
[43:36.280 --> 43:39.380]  They use the CALEA interfaces at the cell towers basically.
[43:39.400 --> 43:42.920]  So theoretically you could still pipe a C-tone over a cell phone call and do the exact same thing.
[43:43.260 --> 43:43.500]  Yeah.
[43:43.640 --> 43:50.120]  If the CALEA equipment is that backwards compatible stuff with all the old bugs then it will also work over cell phones.
[43:50.620 --> 43:51.000]  Thanks.
[43:51.340 --> 43:52.180]  Under the local GSM.
[43:54.120 --> 43:55.380]  Under the local GSM.
[43:55.480 --> 43:55.580]  Yeah.
[43:57.280 --> 43:59.120]  So I think we're going forward and back.
[43:59.440 --> 44:05.900]  I'm not going to criticize your exercise just because it ended up being an academic exercise because, hey, I think exercise is good.
[44:06.060 --> 44:06.860]  Well, none of...
[44:06.860 --> 44:07.500]  No, wait a minute.
[44:07.580 --> 44:08.560]  What do you mean academic exercise?
[44:08.780 --> 44:10.060]  None of us have been caught yet.
[44:12.020 --> 44:14.060]  Causation is not correlation, right?
[44:14.780 --> 44:24.460]  But isn't it true that the law enforcement is going to obviously see that something's wonky here and they're going to reconcile via the timestamps with the call records that the CO has to have?
[44:24.460 --> 44:25.760]  Funny you should ask.
[44:26.780 --> 44:27.900]  Funny you should ask.
[44:28.180 --> 44:31.260]  So one of the things we did was looked at...
[44:31.260 --> 44:43.540]  One of the things that happens at a trial when they introduce law enforcement... law enforcement introduces wiretap evidence is they bring in an expert because there are all these funny sounds on it and there are these confusing-looking records.
[44:43.900 --> 44:49.780]  They bring in an expert from the wiretap bureau to kind of explain what's going on in the wiretap.
[44:49.780 --> 44:55.820]  So we spent some time looking at trial transcripts where wiretap evidence has been introduced.
[44:56.020 --> 44:59.020]  And we cite a couple of the cases in our paper on this.
[44:59.300 --> 45:07.180]  Apparently, fairly routinely, the wiretap expert gives testimony along the lines of, yeah, that's a C-tone.
[45:07.480 --> 45:08.800]  That noise is a C-tone.
[45:08.940 --> 45:09.540]  Just ignore it.
[45:09.600 --> 45:11.020]  They pop up every now and then.
[45:11.160 --> 45:13.320]  We don't quite know why it happens.
[45:14.380 --> 45:18.340]  But it just seems to be how the equipment... the equipment's kind of old and flaky.
[45:18.340 --> 45:31.620]  So we don't actually know... First of all, we do know how law enforcement agencies react when confusing things happen, which is to just attribute them to the phase of the moon.
[45:33.580 --> 45:37.220]  What we don't know is whether or not we were the first to discover this.
[45:37.680 --> 45:43.940]  Because when wiretaps are incomplete or weird, they don't seem to be getting investigated.
[45:43.940 --> 45:46.980]  Now, I came across the paper on Dan Kaminsky's blog.
[45:47.200 --> 45:48.040]  It's an excellent paper.
[45:48.180 --> 45:49.420]  I think you should throw the URL up there.
[45:49.540 --> 45:51.820]  I think everyone would benefit from checking it out.
[45:51.940 --> 45:52.160]  Thank you.
[45:53.120 --> 45:54.340]  So Google knows.
[45:54.480 --> 45:55.740]  So Google wiretaps.
[45:55.900 --> 45:56.980]  And you'll find us.
[45:59.380 --> 46:07.860]  A couple of my questions were already answered, but the call minimize button just seems so incredibly quaint.
[46:07.860 --> 46:22.100]  I mean, everybody has to be thinking about, like, Casino, where, you know, the two wives get on the phone, and then after a certain period of time, the, you know, gangsters yank the phone out of their hand, and they start talking.
[46:22.200 --> 46:26.460]  I mean, are you really saying that still to this day, even after the PATRIOT Act...
[46:26.460 --> 46:27.280]  That's a legal requirement.
[46:27.560 --> 46:33.840]  ...they don't bother to cut back into the phone call at any point to monitor whether or not...
[46:33.840 --> 46:40.320]  The thing is that what the C-tone does effectively is pushes the minimize button for them.
[46:42.320 --> 46:54.940]  Yeah, but I'm just saying, in general, you were saying, like, for instance, if, you know, the two of you lived in the same house, and they wanted to listen to you, but they didn't want to listen to her, and so they answered...
[46:55.400 --> 47:00.180]  She made a phone call, and they heard it was her voice, and so they just decided to turn that off.
[47:00.180 --> 47:03.720]  And then, after a minute, you took the phone out of her hand and started talking.
[47:03.800 --> 47:05.480]  They would never know, even to this day.
[47:05.560 --> 47:09.420]  I'm not sure how often they check in again, but it's every minute or two that they...
[47:09.420 --> 47:16.900]  And do you have any idea, according to, like, the stipulation of the law, like, how long they can listen before they have to turn that thing off?
[47:17.000 --> 47:21.000]  As soon as they figure out that it's not the target talking, they are required to stop listening.
[47:21.180 --> 47:23.640]  And after some interval, they can go and start listening again.
[47:24.260 --> 47:27.020]  There's a DOJ manual on the Department of Justice website.
[47:27.020 --> 47:28.460]  It tells the exact interval.
[47:28.620 --> 47:30.460]  I don't remember what the number is, but...
[47:30.460 --> 47:30.820]  I see.
[47:30.940 --> 47:45.300]  And just to sort of follow up on his question about cell phone tapping, they wind up, regardless of the technology employed, whether it's GSM or EVD, you know, CDMA, it's the same sort of CALEA interface?
[47:45.580 --> 47:51.640]  The CALEA interfaces, cell phones were one of the reasons they put the CALEA interfaces in, because they didn't want to have to do over the air tapping.
[47:51.780 --> 47:56.500]  They wanted to be able to go to the phone company and just get a standard interface out of them.
[47:56.500 --> 47:57.560]  Okay, thanks.
[47:58.120 --> 48:01.820]  So I think we have time for like one more... or zero more questions.
[48:02.020 --> 48:02.520]  One more question.
[48:03.180 --> 48:03.460]  One more.
[48:03.460 --> 48:11.520]  If I'm at work and I'm on a PBX at the office, I was wondering, can my manager eavesdrop my phone call?
[48:11.620 --> 48:20.280]  Do PBXs from seven years ago, do they have a mechanism to allow higher-level people to listen in on a PBX call?
[48:20.280 --> 48:25.120]  So I know that, you know, often call centers often have that functionality built in.
[48:25.240 --> 48:34.460]  And one of the side businesses that the makers of the law enforcement wiretap equipment has is often the equipment for that kind of monitoring.
[48:34.820 --> 48:37.320]  Normal run-of-the-mill office PBXs, I'm not sure.
[48:40.240 --> 48:40.720]  Thanks.
[48:40.720 --> 48:41.260]  Thank you.