By Benjamin Smith
The Supreme Court’s 2012 decision in US v. Jones failed to resolve many open questions in Fourth Amendment privacy protection, including the particularly shadowy domain of International Mobile Subscriber Identity (“IMSI”) catchers. IMSI catchers, colloquially called “stingrays”, are devices used by law enforcement agencies to monitor cell phone conversations, for which ordinary wiretaps are not feasible, without going through telecommunications providers. IMSI catchers work by fooling a cell phone into thinking the catcher is a local cell tower. It can then force the cell phone to use insecure channels even if otherwise set to encrypt its conversations. Once the IMSI catcher has routed the cell phone onto an insecure channel, any conversation may be easily monitored and recorded.
There are two major Fourth Amendment concerns with IMSI catchers. First, it is unclear whether the use of an IMSI catcher qualifies as a search. Some might have hoped a case like US v. Jones to come close to resolving the question, but it did not. It seems unlikely that use of an IMSI catcher would not be ruled a search, but IMSI catchers are currently routinely used without a warrant. Judges have begun to push back against the warrantless use of IMSI catchers, including in the ongoing US v. Rigmaiden case in the District of Arizona, but such resistance is only in its earliest days.
In addition, when an IMSI catcher is activated, it does not target a specific cell phone but instead draws in all cell phones operating nearby. If an IMSI catcher records all conversations, conversations will be recorded equally from innocents as from suspects. Thus, even if law enforcement is using an IMSI catcher only under a warrant and with court approval, unintended intrusions without a warrant are bound to occur. The security of such data collected from innocents is unclear.
As the technology becomes cheaper and more widely available to law enforcement agencies, privacy questions about IMSI catchers will have to be resolved. In the mean time, remember it as an emerging technology with unusual privacy implications.
Additional information on IMSI catchers is available below:
http://online.wsj.com/article/SB10001424052970204621904577014363024341028.html
http://gritsforbreakfast.blogspot.com/2013/03/bypassing-telecoms-stingrays-allow.html