IMSI-catcher

An international mobile subscriber identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking location data of mobile phone users. Essentially a 'fake' mobile tower acting between the target mobile phone and the service provider's real towers, it is considered a man-in-the-middle (MITM) attack. The 3G wireless standard offers some risk mitigation due to mutual authentication required from both the handset and the network. However, sophisticated attacks may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication. An international mobile subscriber identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking location data of mobile phone users. Essentially a 'fake' mobile tower acting between the target mobile phone and the service provider's real towers, it is considered a man-in-the-middle (MITM) attack. The 3G wireless standard offers some risk mitigation due to mutual authentication required from both the handset and the network. However, sophisticated attacks may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication. IMSI-catchers are used in the United States and other countries by law enforcement and intelligence agencies, but their use has raised significant civil liberty and privacy concerns and is strictly regulated in some countries such as under the German Strafprozessordnung (StPO / Code of Criminal Procedure). Some countries do not have encrypted phone data traffic (or very weak encryption), thus rendering an IMSI-catcher unnecessary. A virtual base transceiver station (VBTS) is a device for identifying the international mobile subscriber identity (IMSI) of a nearby GSM mobile phone and intercepting its calls. It was patented and first commercialized by Rohde & Schwarz in 2003. The device can be viewed as simply a modified cell tower with a malicious operator, and on 4 January 2012, the Court of Appeal of England and Wales held that the patent is invalid for obviousness. The GSM specification requires the handset to authenticate to the network, but does not require the network to authenticate to the handset. This well-known security hole is exploited by an IMSI catcher. The IMSI catcher masquerades as a base station and logs the IMSI numbers of all the mobile stations in the area, as they attempt to attach to the IMSI-catcher. It allows forcing the mobile phone connected to it to use no call encryption (A5/0 mode) or to use easily breakable encryption (A5/1 or A5/2 mode), making the call data easy to intercept and convert to audio. The 3G wireless standard mitigates risk and enhanced security of the protocol due to mutual authentication required from both the handset and the network and removes the false base station attack in GSM. Some sophisticated attacks against 3G and LTE may be able to downgrade to non-LTE network services which then does not require mutual authentication. Body-worn IMSI-catchers that target nearby mobile phones are being advertised to law enforcement agencies in the US. IMSI-catchers are often deployed by court order without a search warrant, the lower judicial standard of a pen register and trap-and-trace order being preferred by law enforcement. They can also be used in search and rescue operation for missing persons. Police departments have been reluctant to reveal use of these programs and contracts with vendors such as Harris Corporation, the maker of Stingray and Kingfish phone tracker devices. In the UK, the first public body to admit using IMSI catchers was the Scottish Prison Service, though it is likely that the Metropolitan Police Service has been using IMSI catchers since 2011 or before. Every mobile phone has the requirement to optimize the reception. If there is more than one base station of the subscribed network operator accessible, it will always choose the one with the strongest signal. An IMSI-catcher masquerades as a base station and causes every mobile phone of the simulated network operator within a defined radius to log in. With the help of a special identity request, it is able to force the transmission of the IMSI.