Security: how to know if your SIM has been cloned or hacked

There are a few main reasons why someone would want to clone / hack a SIM card:

1. Get access to two-factor authentication codes sent via text message. This would allow the hacker to access important online accounts that would otherwise be protected, such as online banking.
2. To receive messages and calls from another person, etc. This could be due to a variety of reasons, including spying on their communication activity and contact with others.
3. To impersonate another person. If someone has cloned another person's SIM card, he not only has the ability to receive incoming messages and calls, but can also send outgoing messages and calls using his own number. This means that they could impersonate them to gain access to important accounts or even scam the victim's contacts.
4. To target a high-value individual. Hackers often target people with a certain business position or a certain level of wealth using this technique. Like the recent example of Twitter's billionaire CEO Jack Dorsey, a victim of a SIM card hacking technique known as “SIM Swapping”.

So, is it possible for someone to hack or clone your SIM card?

The short answer to this is yes. It is absolutely possible for someone to clone or even hack your SIM card.

However, it's not that common - in fact, installing spyware on a victim's device is a much more common practice used by hackers. It is also a popular misconception that hackers can "tap into" your SIM card to listen to calls, read texts, etc. Without you knowing. The reality is that it's very easy to tell if your SIM card has been hacked or cloned.

Overall, compared to traditional spyware, SIM card hacking / cloning is not as effective, it is much more difficult to perform and it is much more easily detectable by the victim. Furthermore, the spyware installation allows the hacker to gather other important information besides calls and text messages from the user's phone.

How to know if your SIM card has been hacked

There are several (usually very simple) ways to detect if your SIM card has been cloned or hacked:

1. You no longer receive calls and messages. If someone has cloned your SIM card or convinced your network operator to transfer your number to a new SIM card they have, you will no longer receive text messages or phone calls. A phone number can only be associated with one SIM card at a time. You can easily verify this by asking a friend to call or text you and if it doesn't come then you know you may have a problem. Note: If you are still able to receive calls and text messages, your SIM has not been hacked or cloned.
2. Unrecognized numbers on your account. If you're checking outgoing calls on your bill and see numbers you don't recognize, it might be time to contact your network operator and try to get more information.
3. You receive a message asking you to restart your device. One of the very first signs of SIM hacking you will notice is a seemingly random text purporting to come from your network provider asking you to restart your device. It is usually a message sent by the hacker. Restarting the phone gives them the option, while the phone is off, to steal your SIM details.
4. The device appears in a different location on the location trackers. If you're using something like Find My iPhone for iOS or Google's Find My Device for Android, this can be a good way to check for SIM issues. If your phone appears in a different location, this is a sure sign that your SIM card has been compromised and is being used by a hacker. Note: In many cases, hackers will simply disable this setting.