Government has prohibited imports of all kind of mobile handsets with fake or duplicate unique identity numbers, a move that will help security agencies in tracking callers using different SIM cards. "GSM mobile handsets with duplicate IMEI or fake IMEI & 'CDMA mobile handsets' with duplicate ESN (Electronic Serial Number)/MEID (Mobile Equipment Identifier) or fake ESN/MEID are added to the list of 'Prohibited' items for import," Director General of Foreign Trade said in a notification. An IMEI number — a 15-17 digit number unique to mobile phones that use the GSM technology platform — is used to identify a device on a cellphone network.