Rogue cell towers
Coeur d'Alene Press | UPDATED 11 years, 7 months AGO
Dear PropellerHeads: I've heard that there are rogue cell towers just listening to whoever might pass by for purposes unknown. Science fiction or science fact?
A: While many things I see on television and in the movies give rise to orbital-level eye rolls (invalid IP addresses, ludicrous image enhancement, visual fingerprint matching), this is actually very real and getting more and more attention from privacy advocates.
The official name is an IMSI-catcher. The slang term is a Stingray, which is the name of one of the more well-known IMSI-catchers. Strangely, the product is not listed anywhere on the company's website (www.harris.com).
IMSI is the acronym for International Mobile Subscriber Identifier. It is tied to the phone's SIM card and is roughly equivalent to a MAC address for any device connecting to the Internet. It is used to determine which cell towers in the area are preferred by the phone in order to prevent roaming charges.
However, these IMSI-catchers are rarely adhered to an actual tower. They are more often light and portable, with even some handheld models. One has already been made from a Raspberry Pi.
IMSI-catchers work because of a core principle in cell network functionality. In cases where there are multiple towers that a cell phone could connect to, it will always connect to the one with the strongest signal. Makes sense. But then, all an IMSI-catcher needs to do is have a stronger signal than any nearby legitimate cell tower.
The other loophole that allows IMSI-catchers to function is that in the case of GSM networks, only the phone needs to authenticate itself to the network, the reverse is not required. Put these two things together and you essentially have en masse wiretapping.
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