!!! Overview[1]
[{$pagename}] ([SIM]) is an [Smart Card] that is intended to securely store the [International Mobile Subscriber Identity] ([IMSI]) number and its related key, which are used for [Identification] and [authenticate] [subscribers] on [Mobile Device] (such as Mobile phones and computers).

[{$pagename}] [Universal Subscriber Identification Module] ([USIM]) and [Universal Integrated Circuit Card] ([UICC]) has replaced the [SIM] for most purposes for [{$applicationname}] may be and are often used interchangeably.

[{$pagename}] is also possible to store contacts on many [{$pagename}] cards. 

[{$pagename}] cards are always used on [GSM] phones; for [CDMA] phones, they are only needed for newer [LTE]-capable handsets.  [{$pagename}] cards can also be used in [satellite] phones.

[{$pagename}]s are designed to be transferable between different [Mobile Devices]. 

!! Structure and [File Systems]
[{$pagename}] contains a processor and [Operating System] with persistent, electronic erasable, programmable read-only memory ([EEPROM]). [{$pagename}] also contains [RAM] and [ROM]. 

[RAM] controls the program execution flow and the [ROM] controls the [Operating System] workflow, user [authentication], data [encryption] [algorithm], and other [applications]. 

The [Hierarchical] organized [File System] of a [{$pagename}] resides in persistent [memory] and stores [data] as names and phone number entries, text messages, and network service settings. The [File System] consists of three types of files: 
* master file (MF)
* dedicated files
** DF (DCS1800)
** DF (GSM)
** DF (Telecom)
* elementary files - EF ([ICCID])
The master file is the root of the [File System]. Dedicated files are the subordinate directories of master files. Elementary files contain various types of [data], structured as either a sequence of data bytes, a sequence of fixed-size records, or a fixed set of fixed-size records used cyclically.

!! [{$pagename}] [Security]
A [SIM] card contains a unique serial number ([ICCID]), [International Mobile Subscriber Identity] ([IMSI]) number, security [authentication] and ciphering information, temporary information related to the local network, a list of the services the user has access to, and two [passwords]: 
* [Personal Identification Number] ([PIN]) for ordinary use, 
* [Personal Unblocking Code] ([PUK]) for [PIN] [unlocking|Credential Reset].

[SIM] cards have built-in [security] features. The three file types, MF, DF, and EF, contain the security attributes. These security features filter every execution and allow only those with proper [authorization] to access the requested functionality. There are different levels of [Access Control] in DF and EF files. They are:
* Always—This condition allows to access files without any restrictions.
* Card holder verification 1 ([CHV1])—This condition allows access to files after successful verification of the user’s [PIN] or if [PIN] verification is disabled.
* Card holder verification 2 ([CHV2])—This condition allows access to files after successful verification of the user’s [PIN2|PIN] or if the [PIN2|PIN] verification is disabled.
* Administrative (ADM)—The card issuer who provides SIM to the subscriber can access only after prescribed requirements for administrative access are fulfilled.
* Never (NEV)—Access of the file over the [SIM]/ME interface is forbidden.
The [SIM] [Operating System] uses [Access Control] to an element of the [File System] based on its access condition and the type of action being attempted. The [Operating System] allows only limited number of attempts, usually three, to enter the correct [CHV] before further attempts are blocked. For unblocking, it requires a [PUK] code, called the PIN unblocking key, which resets the CHV and attempt counter. If the subscriber is known, then the unblock [CHV1]/[CHV2] can be easily provided by the [Mobile Network Operator].!! [Security Considerations]
The [SIM] and [UICC] card contains sensitive information about the subscriber. [Data] such as contact lists and messages can be stored in [{$pagename}]. SIM cards themselves contain a [repository] of [data] and information, some of which is listed below:
* [Integrated Circuit Card Identifier] ([ICCID])
* [International Mobile Subscriber Identity] ([IMSI])
* Service provider name (SPN)
* [Mobile Country Code] ([MCC])
* [Mobile Network Code] ([MNC])
* [Mobile Subscriber Identification Number] (MSIN)
* [Mobile Station International Subscriber Directory Number] (MSISDN)
* Abbreviated dialing numbers (ADN)
* Last dialed numbers (LDN)
* [Short Message Service] ([SMS])
* Language preference (LP)
* Card holder verification ([CHV1] and [CHV2])
* Ciphering key (Kc)
* Ciphering key sequence number
* Emergency call code
* Fixed dialing numbers (FDN)
* [Location Area Identity] ([LAI])
* Own dialing number
* [Temporary Mobile Subscriber Identity] ([TMSI])
* Routing area identifier (RIA) network code
* Service dialing numbers (SDNs)

There have also been some [Vulnerabilities|Vulnerability]
* [SS7 hack] - is related to [SIM Swap]

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Subscriber_identity_module|Wikipedia:Subscriber_identity_module|target='_blank'] - based on information obtained 2016-08-15