A SIM swap attack is an example of fraud in which someone tricks a mobile phone carrier into transferring or associating the victim’s telephone number with a SIM card used by the attacker. When the criminal controls the victim’s phone number, they can easily intercept SMS and voice messages.
In this article, we’ll learn how SIM swap attacks can severely compromise sensitive accounts and information. Knowing the risks and taking preventative measures may help reduce their impact.
The attack begins by gathering personal information about the targeted person, such as names, addresses, phone numbers, account information, and sometimes even passport or ID details. This data can be obtained through different means, such as phishing attacks, social engineering, or directly from the information the victim shares on social media.
SIM Swap attack
After obtaining the personal information, the attacker contacts the mobile network provider to convince them to transfer the victim’s number to a new SIM card.
Once the network provider transfers the phone number to a new SIM card, the victim’s phone loses its services while giving attackers all necessary controls. The attackers acquire the ability to reset passwords of online accounts that depend on such phone number for account recovery or two-factor authentication.
If the attacker gains control over your phone number and, by extension, the accounts and services attached to that number, the consequences can be extremely severe.
Bank account access. An attacker who gains access to your bank account through password resets or one-time passwords sent via SMS might wire money out of your account, make unauthorized payments on your behalf, or sometimes even apply for loans you don’t need.
Identity theft. The attacker may access personal information stored in your email, social media, or other online accounts, which could be used for further identity theft or sold on the deep web. You could face legal issues if the attacker uses your identity for illegal activities.
Account takeover. By changing passwords, the attacker can lock you out of your email, social media, and other important accounts. The loss could be permanent if the attacker deletes data, such as emails, contacts, or social media posts, especially if you don't have backups.
An attacker could invade your privacy by reading your text messages, listening to your voicemails, and even pretending to be you in calls or messages.
Dealing with a SIM swap attack can be a real hassle and take up a lot of time. You'll need to regain access to your accounts, keep an eye out for identity theft, and possibly recover any lost money or data. The effects aren't just about the financial or privacy issues; it can also take a toll on your emotional health and personal relationships.
Reducing the impact of this kind of attack can be obtained through early detection. If you see any of these signs, it could mean that your phone or number was involved in a SIM swap attack:
The most common sign of a SIM swap attack is the loss of cellular service. Your phone may no longer make calls, send texts, or access data as it used to. You might see messages like “no sim card” or “emergency calls only.”
You notice unusual activity in your account, such as changing passwords, adding new devices, or changing security settings. Another red flag could be unfamiliar transactions or withdrawals from your bank account.
Unable to access your accounts, even if you use the correct credentials, could mean an attacker has already changed your password.
If you notice any of the signs described above, it's essential to act quickly:
The first thing you should do is contact your mobile network provider immediately. Inform them of the situation and ask them to restore your number to your original SIM card. If possible, ask them to secure your account with additional measures, like a PIN or password.
It is very important to report the incident. Notify your bank or credit card company, and consider reporting the incident to local law enforcement and a fraud reporting agency. This will help to avoid potential legal consequences if attackers use your identity for illegal activities.
Update the passwords for all important accounts, especially those linked to your phone number. Review the security settings of your accounts, remove any unfamiliar devices, and check for unauthorized changes.
Monitor financial accounts. Check your bank accounts and credit card statements for suspicious activity.
We can take several measures to prevent a SIM swap attack:
Contact your mobile carrier to request to set up a unique PIN or password that must be provided before any changes can be made to your account, including SIM swaps.
Always use strong passwords: Avoid using easily guessable passwords. Using a password manager is always a good idea, so you don’t have to remember passwords anymore.
Enable two-factor authentication (2FA) methods that don't rely only on SMS, such as email, authentication apps or hardware tokens.
Change your online behavior. Everything you post or share on the Internet could be used to launch an attack. Avoid disclosing personal information such as birth date, address or phone number.
Be careful with phishing scam messages or calls requesting your personal information. Always verify the source before providing any details.
Secure your mobile device. Unlock your phone using a PIN, password, fingerprint, or facial recognition. This helps prevent unauthorized access if your phone is lost or stolen.
These steps can significantly reduce your chances of falling victim to a SIM swap attack. While nothing is entirely foolproof, using strong authentication, keeping a close eye on your accounts, and following secure practices can make it much more challenging for attackers.
If your company relies on users’ phone numbers for activities such as two-factor authentication (2FA), password resets, or login processes, you can improve security and reduce fraud using APIs like the Vonage SIM Swap API.
The SIM Swap API helps to mitigate account takeover risks by checking if the SIM card linked with a phone number has recently changed. This is particularly useful for identifying suspicious activity before sending an SMS during the two-factor authentication (2FA) process. If a recent SIM swap is detected, you can, for example, switch to an alternative verification method, such as email.
Is your company using the phone number for any account activities? How do you ensure sending them an SMS when resetting passwords is safe? We’d love to hear your feedback! Join us on the Vonage Community Slack or message us on X, and we will get back to you.
Thanks for reading!
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Alvaro is a developer advocate at Vonage, focusing on Network APIs. Passionate about Developer Experience, APIs, and Open Source. Outside work, you can often find him exploring comic shops, attending sci-fi and horror festivals or crafting stuff with those renowned tiny plastic building blocks.
