SIM security

What is a UICC card?

The Universal Integrated Circuit Card (UICC) is the smart card used in mobile terminals in GSM, UMTS, and LTE networks. A UICC card hosts several applications, making it possible for the same smart card to give access to different mobile networks. The UICC contains a Subscriber Identity Module (SIM) application for GSM access, Universal Subscriber Identity Module (USIM) application for UMTS and LTE access, and IP Multimedia Services Identity Module (ISIM) application for IMS multimedia services. A UICC card is a removable tamper-resistant plastic card that houses a small electronic circuit which is used, in turn, to store identification information about your cellular network account. A mobile network will recognize a device as unique based on the unique information on the UICC card.


What information is stored on a UICC card?

A UICC card stores information about your cellular network account, and your devices rights to access a mobile network. A UICC card stores subscriber-related data, such as phone numbers, service details, and memory for storing text messages (depending on the phone.) Many UICC cards also store your contacts information. Most importantly, the UICC card is used to authenticate the phone on the network.


How are UICC cards secured by design?

UICC cards are tamper-resistant, utilize encryption technology and access control measures to secure the data stored on the card. UICC cards also carry an anti-fraud protocol that prevents alteration of data or receiving services that have not been paid for or requested. As with any technology, UICC card security requires constant vigilance against unwanted potential external intrusion. Practicing good security procedures can help to reduce risks that can be posed by unauthorized access.


Things you can do to protect your UICC card and other personal information

1) Set and use a UICC security Personal Identification Number (PIN)
You can lock your UICC with a personal identification number (PIN). A UICC PIN helps to prevent access to the information on your UICC. A UICC PIN also helps prevent someone who does not have the PIN from using your UICC in another phone to make calls. The steps to change and enable a UICC PIN may vary, depending on the device you are using. T-Mobile customers can learn more by searching on T-Mobile’s online support pages, using the search term “UICC PIN” to find the correct procedures for specific devices:, or by calling customer service by dialing 611 from a T-Mobile device.

Note: if your PIN code is entered incorrectly more than three times, the mobile device will require PIN unlock code in order to unlock the UICC.

2) Put a password on your phone and set a screen lock for your device, in addition to enabling a UICC PIN
All phones have security settings so familiarize yourself with them and turn them on, including setting up a password for the device itself. If your phone has not been used for a few minutes, it should automatically lock and require a password or PIN to reactivate. Review your phone’s manual, find help on T-Mobile’s online support pages, or contact T-Mobile customer service to learn how to enable a screen lock or other types of security measures.

3) Encrypt your data
Some phones allow you to encrypt your data, sometimes using third-party software. Encryption secures your data if your phone is lost or stolen. While UICC cards are encrypted by design, encrypting the data stored on your phone creates an added layer of protection.

4) Purchase a UICC card reader
Most of the information on the UICC card cannot be altered and is required for use on your cellular network, but you can control some information. T-Mobile does not retain your text message content, but text messages may remain on the UICC card until overwritten by new data. With a UICC reader, you can view, backup, and physically delete information from the UICC card, including your text messages. UICC card readers can be readily found online, including at, and instructions for use are also easily found online.
Note: The UICC card can be easily damaged by scratches or bending. Use caution when inserting or removing the card from the mobile device.