SIM cloning is the process in which a legitimate SIM card is duplicated. When the cloning is completed, the cloned SIM card's identifying information is transferred onto a separate, secondary SIM card. The secondary card can then be used in a different phone while having all calls and associated charges attributed to the original SIM card. The phrase SIM clone is often used to refer to the SIM card that has been successfully duplicated.
A successful duplication hinges on the a user's ability to extract the SIM card's IMSI (International Mobile Subscriber Identifier) and Authentication key (Ki). While a IMSI is relatively easy to identify, finding the Ki can prove to be much more difficult for the novice user. Separate devices and software programs may have to be used to decrypt the Ki.
Engaging in activities that can result in a SIM clone is illegal. In the 1990s, companies that provided cellular services recognized the problems that SIM cloning presented and began to take measures to thwart the cloning business. New security measures such as embedding security operations make obtaining a SIM clone more difficult. Now, if a SIM card detects that cloning has been engaged, the SIM card can render itself inoperable. Whereas a few years ago cloning could be done by radio, people must now have physical access to the original SIM card.
Though SIM cloning was easier with older models of cell phones and can still be technically done today, successfully completing a cloning is very difficult for some and virtually impossible for most. Most of the technology currently available to facilitate cloning is meant to work only on older models of phones. Anti-tamper software on V2 of 3G SIM cards makes cloning new SIM cards and their corresponding devices a lost effort.
As attractive as obtaining a SIM clone may seem to individuals who desire to use two phones with one phone number, legal and technical difficulties should discourage any efforts to clone SIM cards. It should also be noted that though using a clone can appear convenient in some respects, safety issues may also present themselves as a result of using the clone. Law enforcement agencies may find it difficult to reach an injured or distressed party if an emergency call is made by a phone using a clone. This is because clones compromise the GSM location-based service that SIM cards rely on.