Guide to DIY Wiretapping

Geeks are Sexy writes "ITSecurity.com has a nice piece this week on how wiretapping works and how you can protect yourself from people who wants to snoop into your life. From the article 'Even if you aren't involved in a criminal case or illegal operation, it's incredibly easy to set up a wiretap or surveillance system on any type of phone. Don't be surprised to learn that virtually anyone could be spying on you for any reason.'" Maybe I'm on the wrong track here, but I guess I assumed that wiretapping now happened in secret rooms at the telco, and not by affixing something physically to a wire in your home, but I'll definitely be aware next time I hear a stranger breathing next time I'm stuck on hold.

Comments

voltage drop

[omeomi]

Most of the land line suggestions in that article don't seem to bother with taking care of the noticeable voltage drop caused by adding an extra phone to a call. You can tell when somebody else in your house picks up the phone while you're on it because the person on the other end gets quieter. The same thing would happen if you plugged a phone into the line outside your house. I thought professional surveillance systems did something to make up for this, so there's no noticeable change in volume when the wiretapper starts listening.

Re:voltage drop

[bugnuts]

The Ringer Equivalence Number is just the number of phones the ringer can drive. More than that, and they won't have the voltage to ring.

It has nothing to do with talking on the phone.

What you'd want to do is use an inductive microphone or even an inductive loop around the actual cable. It doesn't touch it, and is very difficult to detect if it's nearby the cable... Search for the USS Halibut, and how it tapped a Soviet military underwater cable by using a nearby inductive coil which never interfered with the cable.

Re:voltage drop

[mollymoo]

If you use a normal phone, yes. Until recently I worked in telecoms and we were all issued with a near perfect bugging device - a butt phone with monitor mode. Monitor mode is high-impedance so undetectable without some clever kit. Connect it to the right pair, hit the button and you can listen in undetected at will. You can buy one for a hundred quid ($200) or so, probably less if you shop around. Monitoring lines was standard practice, albeit briefly, when working on a line - you listen to make sure nobody is using the phone, then dial a test number using the line to make sure it's the right circuit, then do whatever you need to do. You aren't supposed to listen to people's conversations, merely ensure the line isn't in use, but that doesn't mean it didn't happen.

Telecoms cabinets aren't all that secure, it's easy to break in and put a tap in one and with a little care it wouldn't be obvious to an engineer working in the cabinet there was anything amiss. You could make a tap with a microcontroller with an ADC and some external RAM. The hard part would be finding the right pair without access to the phone company records or target's premises.

Re:It was..

[N1ck0]

Of course you can still tap any POTS line the good old fashion way. Its just a matter of accounting for the voltage drop on the line. Although yes if you are the telco it is just easier to capture everything while it is in digital format on the switch. Now if you don't use analog, inline (some random place between the CO and customer) tapping can be a bit harder. You basically either have to record the signals on the line and decode it later, or toss a non-terminating CSU/test kit in the line without making too much of a disruption in the signal.

WTF??

[f8l_0e]

The article also links to this product. They never had toys this fscking cool when I was a kid.

stop glossing over Skype's problem

[Sloppy]

Countermeasure suggested by article:

Use an encryption VoIP service like Skype: Skype is an especially difficult service to tap, because of its encryption strategy. Slate reporter David Bennahum writes that "the company has built in such strong encryption that it's all but mathematically impossible with today's best computer technology to decode the scrambled bits into a conversation." You're more protected with this system.

I sometimes feel bad about flaming Skype. They really are more resistant to eavesdropping than most everything else, and it's nice they used AES256. They almost got it right.

But saying it's mathematically impossible to crack 'em is bullshit, because Skype's design is flawed (in at least one way that we know of -- and there's a lot we don't know about it, because it's closed and hasn't been really audited by crypto-nerds -- that's Skype first problem). AES256 is useless if the key itself has been compromised by MitM, and Skype's design allows that (that's Skype's second problem). Skype depends on a central server to introduce identities to one another, and that central point is potentially subject to compromise (or coercion). There's no reason VoIP users can't (in many cases, at least) cert each other directly, but unfortunately, that's not how Skype works.

Skype can be tapped, and all this talk about how its heavy crypto prevents that, is a smokescreen. AES is believed to be a strong link in this chain, but don't forget that we're talking about a chain.

Re:You don't need a phone to listen in..

[Em Adespoton]

Not recommended, but I used to use a 9VDC battery in a circuit to boost signal in the local circuit back when I was on a party line. It seemed to provide the boost needed and the telco never complained. I never did figure out why it worked, considering analog twisted copper does run AC.