IMSI stands for International Mobile Subscriber Identity, and an IMSI number uniquely identifies a mobile device to a network operator. The IMSI is contained in the devices’ SIM card.
An IMSI Catcher is a technology that utilizes a software-defined radio, filters, amplifiers, and other components to replicate a mobile base station, usually in a smaller form factor.
An IMSI Catcher, sometimes called Stingrays, false base stations, cell site simulators, etc. have all been used in recent press articles that have highlighted criminal activities of using such devices to send illicit SMS’s to multiple mobile devices in a range of equipment to look to undertake smishing scams or mentioned by data privacy groups for the concern of oppressive governments using such equipment to monitor and track people illegally.
The IMSI Catcher technology is classed as dual-use which means goods, software, and technology that can be used for both civilian and military applications. Legitimate providers of such technology in the UK require export licenses from the UK government to enable them to sell such technology.
But do IMSI Catchers deserve only such bad press?
Well, let’s put some misnomers to rest…
IMSI Catchers do not…
o Intercept voice calls
o Retrieve sensitive data from a phone
o Interfere with surrounding network communications
o Interfere or impact someone making an emergency call
o see WhatsApp messages or Facebook or any other data-orientated applications data
IMSI Catchers do…
o Collect device IMSI’s in range of the unit
o Alert on hot listed IMSI’s
o Communicate with the captured device in the case of search and rescue
o Replicate a mobile base station
o Map the location of the IMSI’s captured graphically
o Scan all networks and frequencies
o Need regulatory permission to use
o Require an export license to sell
Yes, in the wrong hands
They can be used for illicit purposes
o To spam devices in range with SMS messages and voice calls
o They can kick your device off your home networks
o They can knock your phone from 5g, 4g to 2g and undertake a silent call which would prevent the end user from making a traditional voice call
In the right hands
Built to high professional and quality standards can be used for good
o Finding people lost in remote areas
o Finding vulnerable people at risk of life
o They can be used in counter-terrorism operations
o They can be used for counter-IED activities
o They can be used to identify human traffickers
o They can be used in the fight to halt organised crime
o They can be used to prevent witness intimidation
o Used in natural disasters to locate victims
o And much, much more