Once a mobile phone has affiliated, the network allocates a
temporary IMSI (TIMSI), which is used to identify the
subscriber in future exchanges. This provides limited anonymity, or privacy.
In order to track a user ina GSM network, an
eavesdropper must intercept the original exchange between the network and
mobile .phone as well as all subsequent exchanges in which
the value of the temporary IMSI (TIMSI) is changed.
Other topics in our resources on GSM related to Temporary IMSI include: