Come January 6 and as many as 25 million mobile phones could be disconnected by the telecom operators.

Concerned about the terrorist attacks in the recent past, the department of telecom (DoT) has asked service providers to disconnect handsets that do not have an international mobile equipment identity (IMEI) number.

IMEI is a unique 15 digit code that identifies a mobile. It prevents the use of stolen handsets for making calls and allows lawful interception to prove the use of a particular device.

The IMEI number appears on the operator’s network whenever a call is made. DoT has asked the service providers to equip networks with Equipment Identity Register (EIR) to check whether calls are made from genuine handsets.

“In the interest of national security, all cellular mobile service providers in unified access service licences (UASL) are hereby directed to make provisions for EIR so that calls without IMEI or with IMEI consisting of all zeroes are not processed or rejected,” DoT said in a letter to operators on October 6.

“If switches do not have such a facility, the necessary hardware and software should be put in place within three months of the issue date of this letter and compliance reported,” it added.

Indian Cellular Association (ICA), the industry body for handset makers, believes that illegal IMEI handsets are being used as there is no validation of IMEI numbers in mobiles entering the country either through sea or air.

Moreover, there is no central mechanism to prohibit the use of stolen phones. The bulk of grey market phones, predominantly originating from China, do not have genuine IMEI numbers. ICA estimates around 25 million such handsets in the country.

However, some operators ET spoke to expressed their inability to meet the DoT deadline due to technical reasons. “What the DoT is trying to do is to block all calls with zeroes as IMEI numbers or from blacklisted numbers. That adds an extra load on networks. There are so many combinations of non-genuine IMEI numbers that it is extremely difficult to block them. Network upgradation is required to block all such calls and not all our multiple equipment vendors are equipped to do it,” a senior official told ET.

He further explained that interrogating all calls would delay call set-up time. “Switches will interrogate most of the time and may not be able to process any calls,” he added.

Another top official at a telecom firm said the move will affect customers who unknowingly bought mobiles without IMEI or whose numbers have been duplicated by others. “The duplicate devices currently being used will not last beyond two-three years. The way out is to check imports to stop entry of handsets without genuine IMEI into India,” he added.