An IMSI cathcher is a highly intrusive piece of technology that locates and tracks all mobile phones that are switched on and connected to a network in a given area.
It does this by pretending to be a mobile phone tower, tricking your phone into connecting to it, and then revealing your personal data without your knowledge.
Some IMSI catchers can even be used to monitor your calls and edit your messages without your knowledge.
“IMSI” stands for “International Mobile Subscriber Identity”, a number unique to your SIM card. Once your phone is tricked into connecting to an IMSI catcher, it reveals this number. the police can use this to easily determine your identity.
HOW DOES AN IMSI CATCHER FIND OUT MY LOCATION?
An IMSI catcher can determine your phone’s general location by measuring the strength of the signal from the phone. And doing this from different locations gives and even more precise fix on the phone’s whereabouts.
CAN AN IMSI CATCHER SNOOP ON MY CALLS & TEXT MESSAGES?
Some IMSI catchers can intercept your text messages, calls and internet traffic. This means other people can read or listen to your personal communications.
Some can even re-route or edit messages, calls and data sent to and from your phone.
And some can also block service so you can no longer use your phone to make or receive calls and text messages – even for emergency numbers.
WHO IS USING IMSI CATCHERS?
When asked, the police “neither confirm nor deny” that they use IMSI catchers. But Liberty and Privacy International are taking the government to court to try and force it to disclose records about its purchase and use of IMSI catchers. This means that they are refusing to explain to the rest of us how they could use these invasive devices to secretly access data from our mobile phones. However, documents obtained by the Bristol Cable and Motherboard show that the following police forces have already bought or have made plans to buy IMSI catchers:
• Avon & Somerset Police • Essex Police • Kent Police • The Metropolitan Police • South Yorkshire Police • Staffordshire Police • Warwickshire Police • West Mercia Police • West Midlands Police
WHAT DOES THE LAW SAY?
It is still unclear whether any law exists that says the police are allowed to use IMSI catchers.
WHAT ABOUT MY RIGHTS?
The police’s use of IMSI catchers is an enormous invasion of your right to privacy. IMSI catchers trick all mobile phones within a certain area into giving up information about their owners – even during what the police say are “targeted” operations looking for specific people. They hoover up your data, but the police refuse to tell us what they do with it, how long they keep it or who they might share it with. And some IMSI catchers let officers listen to your calls, read your texts and see your internet history – an even more extraordinary invasion of your privacy.
Freedom of expression and assembly
And it’s not just your privacy that’s under threat.
IMSI catchers can be used at political gatherings, protests and sporting events to identify and collect the personal data of everyone there. This will no doubt put people off attending certain events or will cause them to behave differently.