Quote:
Originally Posted by hydraMax
(Post 4635921)
For the truly paranoid: A CS instructor once told me that it is possible to remotely monitor the output of a computer monitor or keyboard with an antenna - by picking up and translating the signals emitted by the equipment.
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Up to a point, this is true. If, for example, you knew that someone pressed the 'Q' key, would that help a lot (without, for example, knowing where on the screen it went, which screen the user was looking at, which program the user was using? Further, if you didn't really know that the user pressed a Q, but only that there was an 80 or 95% probability that the key pressed was Q, would that be all that helpful?
This still leaves a relatively high probability that you could get a log in password (quiet-quiet-quiet-qwerty-noisy-noisy-noisy-etc-quiet-quiet-quiet-qwerty has a high probability of meaning that the user types qwerty at the start of their active period, and knowing the log in password could be something that you might be trying to do).
Quote:
Originally Posted by hydraMax
(Post 4635921)
Since then, I have seen this idea used in an episode of Numbers, in which such a device was used to spy on a programmer's computer activity even though he had firewalls, etc. which would have made a real hacking attempt very difficult.
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That's no indication of anything other than some people who don't don't know anything about it thought that it sounded good as a plot point.
Quote:
Originally Posted by hydraMax
(Post 4635921)
What kind of range do they have?
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Depends massively on conditions and error rate that you are prepared to tolerate, but you should be able to achieve 1 cm under all conditions :D Actually, a few metres may often be achievable, and, if you are prepared to use a very, very apparent receiver (imagine a receive antenna of a couple of metres in diameter) you should be easily able to quadruple that.
Let me also point out that you have missed a big point that you should have queried. What chance is there that a piece of snooping equipment optimised for one computer and set of conditions will work with a completely different computer.
No, probably not.
Quote:
Originally Posted by hydraMax
(Post 4635921)
Is it possible to block pre-emptively such surveillance by the use of another device?: I.e., a device that emits interference signals at the same frequencies?
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Yes and no.
Possible, yes, but you may not be able to legally operate such a device, depending on location and whether you prepared to ignore legal niceties.
Usually, the tin foil hat brigade (the tin foil hat goes on the computer this time, and, for once, actually does something other than just reflect light) suggests a tin foil hat at this point. Nice, but the idea that tin foil really suppresses all the emissions is wildly mistaken. It
can be done, to an extent, but go off and buy a 'tempested' computer from a military supplier. You might ask about it, but once you hear the price, you won't buy.
The 'same frequencies' bit is problematic, because, to a greater or lesser extent, that's all frequencies. Some frequencies contain zero information, some contain information of limited utility (eg, is the laptop charging its battery? is the fan on? for most people, having other people know those things isn't something that they care all that much about spending money to avoid, but, if you are a three letter agency, you might wisj to take another view) and some could conceivably be deciphered. You'll need to do the research on the particular target computer to know which frequencies are which.
Probably, there are easier ways of achieving the original objective, but that doesn't put it beyond possibility.