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What is a SIM Clone?

By S. Gonzales
Updated May 16, 2024
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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.

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Discussion Comments
By anon945439 — On Apr 13, 2014

Does anyone knows the measures taken by mobile operators to prevent illegal SIM card swap?

By anon926235 — On Jan 17, 2014

I believe my wife is cheating on me. We have a family plan with two phones and I am the account holder so I can log in and see the texts she sent to the person I believe is involved, but I can only see the timestamp. I was hoping I could clone my sim card that's in her phone and put it in mine so I would also get the texts sent to her at the same time and put an end to this. But it sounds like this is not possible anymore.

I guess I'll have to catch her some other way somehow. It's hard when I work the night shift most of the time.

By anon924641 — On Jan 06, 2014

Why would you clone a SIM? First, for a free second line and second a free second line. Eventually V2 and 3G Sims will be hacked.

By anon354059 — On Nov 05, 2013

I have an iPhone 4 which is about three years old. I have recently purchased an iPad air wifi/cellular. I don't wish to take up a contract with a phone provider. My phone account (which is out of contract) gives me x minutes, unlimited texts and 100mb of data p/m,of which I rarely use more than 50 percent. All I want to do is clone my sim onto a nano sim in order to use my data allowance to its full. Yes I know I can tether my phone to the iPad but it's slow. So what do I do? All (polite) suggestions welcome.

By anon344727 — On Aug 12, 2013

I think someone has illegally made a clone of my sim card. Is there any way of tracking this? I'm not sure how it works or how they would access my messages, etc., but it seems to be happening.

By anon342367 — On Jul 19, 2013

There is a legitimate reason to clone a SIM card: clone two sim cards into one so that you can switch numbers without switching SIM cards for a phone that doesn't support dual SIM cards.

By eidetic — On Nov 27, 2012

@Azuza - You raise a valid point. However, I doubt people who clone phone SIM cards do it because they truly can't afford cell phone service. Some people just get a thrill out of hacking technology of all kinds.

By Azuza — On Nov 26, 2012

Maybe I'm not very tech savvy, but I've never even heard the phrase "clone a SIM card" before. I guess people will always think of new scams for new technology, but I think this one really takes the cake.

It sounds like the purpose for cloning a SIM card would be to avoid paying for cell phone service. However, there are tons of affordable cell phone plans out there, and you could get in a lot of trouble for cloning a SIM card. It seems like it would just be cheaper and easier in the long run to pay for your own phone service!

By dautsun — On Nov 26, 2012

@LoriCharlie - Yeah, I wouldn't even know how to clone a SIM, but installing an app on two phones seems like something most people could handle. So that just leaves the people that want to clone SIM cads for illegal purposes. However, it sounds like that's pretty hard to do, so I doubt SIM cloning happens much these days.

By LoriCharlie — On Nov 25, 2012

@anon148329 - If you have two smart phones, you could also use an app like Google voice. This app lets you pick your own number and gets calls on a smart phone. You could install the app on both phones with the same phone number, and give that number to all your friends. That way, you don't have to mess around with SIM clone software.

Honestly, in this day and age, there is really no legal reason to clone your SIM card. You can get the same results legally and without a lot of effort.

By anon148329 — On Feb 01, 2011

As I researched this topic I realized the simple alternative. Buy a pre-paid sim for your second phone and simply forward one phone to the other.

By anon128519 — On Nov 19, 2010

Vodafone Italy provides a second SIM with your number (a cloned SIM) for free if you are in their 'Top Club" as I am (other users have to pay 2-3 euros for it). It's called "SIM bis". I have two phones with the same number, an Iphone and a dual SIM Samsung.

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