GSM networks are most popular and widespread wireless communication media across the world, having a wide customer base in Europe and Asia-Pacific and command more than 50 percent of mobile customers. The advancement of GSM networks increases rapid growth of its users and services. Being an advance technology it becomes favorites for the criminals. These things created worldwide market for the analysis and monitoring of GSM network.

The advancement of GSM technology, enhanced technological features and increased complexity, presents competitive environment for Stratign to design and develop solutions to provide total Off-The-AIR Communication Surveillance system to its various Government and Intelligence Gathering customers.

GSM operates on standards frequency 850MHz, 900MHz, 1800MHz and 1900MHz bands and offer services such as SMS, MMS, email, advanced video features, dictionaries.

Due to the widespread availability of GSM networks, a GSM mobile has the potential to seamlessly roam nationally and internationally. GSM supports data services where users can send and receive data, at rates upto 9600bps.

The Semi Active GSM Interception System has universal operating capability. This system can be used to intercept communications from any GSM service providers in the world irrespective of the type of encryption being used.

In case of A5/2, the system is completely passive and does not need any Encryption key info to decipher the communication. In case of A5/1, the system comes with a Kc Retriever to obtain the Kc (Ciphering Key) from the network. As soon as the system Semi Active GSM Interception System identifies that the target is communicating using A5/1 encryption, the Kc retriever in the system becomes active.

The Kc retriever automatically acts as a genuine BTS and forces the suspects mobile to register with it, during the periodic location update. The Kc Retriever communicates with the suspects mobile using A5/2 encryption, in the process the Semi Active GSM Monitoring System calculates the Kc. The Kc Retriever also asks the mobile to authenticate itself with its IMSI, by doing so the system also obtains the suspect’s IMSI.

Both the Kc and IMSI information is stored in a database. The Kc Retriever now logoff the suspect’s mobile from its BTS. The Suspect is then allowed to communicate with the Actual Service Provider’s network. With the Kc in the database the system can now decipher all communications encrypted using A5/1.

The Semi Active GSM Monitoring System does not require the service providers SIM for operation. Unlike the other active system where the monitoring agency is billed for the forwarding of target’s calls, which can raise suspicion form the target due to reduced bill amount (since the call charges are borne by the monitoring agency).

The Semi Active GSM Interception System deciphers A5/1 and A5/2 ciphering algorithms online. The number of channels, being received and recorded by the system, can be from 4,6 & 12 for one control computer.