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Some areas of application

The IMSI (international mobile subscriber identity) is a number that uniquely identifies a mobile network user, and it is stored on the SIM card. If the user changes a SIM card, his phone number (MSISDN) is retained, but the IMSI changes. Knowing about a change in IMSI allows you to keep track of any SIM card replacement.

How can this be used? To prevent possible fraud, which is especially important for financial institutions.

For example, before sending a one-time password, the recipient's SIM card is checked to see if it has been changed. If the SIM card has been changed, the message will not be sent. To resume receiving messages, the customer must be verified to ensure that the SIM card has not been taken over by fraudsters.

How IMSI validation works

Putting subscribers on IMSI monitoring
Subscribers that require IMSI tracking are placed under mobile network operators’ monitoring.
SIM card replacement
When the SIM card of a subscriber being monitored is changed, the mobile network operator notifies the Notification Server about the change in IMSI. The subscriber's phone number is placed in the list of numbers that have changed their SIM card.
Sending messages
When sending a message, the recipient's number is searched for in the list of numbers that have changed their SIM card. IMSI check is configured in the template and is available for all communication channels of the Notification Server. If the recipient's number is found in the list whose SIM card has changed, the message will not be sent. Instead, a message is sent telling the subscriber to undergo the identification process, for example, by contacting the call center.
IMSI change confirmation
Having been identified, the subscriber's number is removed from the list of changed SIM cards. After that, the subscriber will resume receiving messages.

Integration with operators

The Notification Server integrates with mobile network operators or messaging aggregators to track IMSI changes.

Protocols for major Russian operators (Beeline, Megafon, MTS, Tele2) and aggregators are supported.


The Notification Server provides a set of services allowing to:
Put a number
on IMSI monitoring

Remove the number
from IMSI monitoring
Delete a number from the list of changed SIM cards (after successful subscriber identification)