As a countermeasure against an NLJD, professional covert listening devices (bugs) of the Central Intelligence Agency were equipped from 1968 onwards with a so-called isolator. An isolator is a 3-port circulator of which the return port is terminated with a resistor. Any energy injected into the bug by an NLJD will be absorbed by the resistor, resulting in no (or very little) reflected energy. An example of such a bug is the CIA's SRT-107.
(or my favorite:)
A means to hinder isolating a non linear junction is to add inexpensive diodes to places where the NLJD is expected to sweep. This masks the true listening device against a field of false alerts when the many diodes are detected. Such a technique was used in the 1980s construction of the U.S. embassy in Moscow. Thousands of diodes were mixed by the Soviets into the building's structural concrete, making detection and removal of the true listening devices by its American occupants nearly impossible.
Are there any bugs that masquerade as normal devices such as phones in a time-frequency sense, such that they blend in the environment as phones. Polymorphic bugs? Bugs that change their signature.
One more question: are there any bugs that shut down if there is no chatter in the spectrum... Say, if it's a noisy environment (frequency wise) with many phones and devices, the bug blends in and transmits. If it gets quiet, such as when phones are being turned off or distant, then there's something fishy and the bug suspends its operation?
They aren't usually off-the-shelf. They're custom, and can be as smart as the builder wants to make them. (working within constraints like size and power supply)
ah. The only documented instances of bugs I know of are in the spy museum in DC, which btw is a fantastic place to visit. The rest, AFAIK, are held close to the vest. I bet there's an amazing museum somewhere inside of the CIA though.
Comments
Yes and no. SS still has an energy signature, which you can recognize if you go looking for SS. And the transmitting antenna can be RDF’ed.
Plus if the electronics aren't shielded you can use a non-linear junction detector even if it's turned off.
Ah, unless your spy is clever....
(or my favorite:)
Rusty nails can also be a false positive. Nothing is perfect but you always have to evaluate your threat profile and mitigate accordingly.
The later scanners filtered out such false positives with extended harmonic analysis.
Are there any bugs that masquerade as normal devices such as phones in a time-frequency sense, such that they blend in the environment as phones. Polymorphic bugs? Bugs that change their signature.
One more question: are there any bugs that shut down if there is no chatter in the spectrum... Say, if it's a noisy environment (frequency wise) with many phones and devices, the bug blends in and transmits. If it gets quiet, such as when phones are being turned off or distant, then there's something fishy and the bug suspends its operation?
They aren't usually off-the-shelf. They're custom, and can be as smart as the builder wants to make them. (working within constraints like size and power supply)
I didn't mean off-the-shelf necessarily. I should have said "are there any documented instances" or something to that effect.
ah. The only documented instances of bugs I know of are in the spy museum in DC, which btw is a fantastic place to visit. The rest, AFAIK, are held close to the vest. I bet there's an amazing museum somewhere inside of the CIA though.