Unstructured Supplementary Service Data (USSD)

Why in news?

• The DoT said that it has come to its notice that USSD based call forwarding facility, most commonly known *401# services for unconditional call forwarding services, is being misused for some unwarranted activities.

About Unstructured Supplementary Service Data (USSD):

• It is a communications protocol used in Global System for Mobile Communications (GSM) networks for sending short text messages.
• It is an instant messaging service and messages are not stored on the operator side or on the subscriber’s device.
• USSD format: It generally exist as one of two types, depending on their origin:
  • A USSD Pull is an outgoing request from the user in the form of an MMI command.
  • A USSD Push is a message from the operator that is displayed on the user’s screen.
  • The user can send the operator a request in the form of a USSD command. Commands consist of the * and # characters and numeric codes.
  • The chain begins with * or # (which can occur more than once, separating commands from subcommands) and usually ends with #.
  • The maximum length of a USSD message is 182 characters, but in practice even the longest requests rarely exceed 20.
• It is used to display balance deduction in mobile phones where a message pops-up on the device screen after a call or outgoing SMS. It is also used for checking IMEI numbers of mobiles.