SIM Card Hacking: What It Is, How It Works, and How to Protect Yourself

How cybercriminals hijack phone numbers to steal PII—and what you can do to stop them

SIM cards might seem like harmless pieces of plastic, but they’re often a gateway for serious cyber attacks. When hackers take over your mobile number, they can intercept private data, bypass security controls, and even drain your bank account.

While most SIM cards only hold basic user data, such as carrier information and contact lists (in older SIMs), cybercriminals have found ways to exploit them—making SIM hacking a fast-growing threat. Here’s how it works and what you can do to stay safe.

Why Do Hackers Target SIM Cards?

SIM cards connect your phone to the mobile network, but they’re also a key to your digital identity. Your phone number is linked to everything from your email to your bank account. That’s why SIM card exploits can open the door to broader system intrusions and identity theft.

Once hackers control your number, they can:

• Bypass multi-factor authentication (MFA) or two-factor authentication (2FA)
• Access sensitive apps and cloud accounts, such as apps that contain running routes, period tracking information, and investments.
• Steal personally identifiable information (PII) or protected health information (PHI)
• Commit fraud or identity theft
• Launch further attacks on your employer or business systems via social engineering.

A personal SIM hijacking incident doesn’t just put an individual at risk—it can serve as an entry point into an organization’s broader digital ecosystem. If a compromised employee or vendor phone is used to access business applications, it can expose internal systems, partner environments, or shared cloud platforms.

Gaining better visibility into supply chains throughout an organization’s cybersecurity ecosystem through Supply Chain Detection and Response (SCDR) can help manage these kinds of risks across your supply chain—before attackers can move laterally or escalate access.

SIM cards pose a unique risk due to their association with sensitive personal data—including medical details, banking credentials, and professional contacts. Their compromise introduces serious data privacy and compliance challenges, particularly under frameworks like GDPR, HIPAA, or PCI-DSS.

3 Major Methods Attackers Hack SIM Cards

1. SIM Swapping

Also known as SIM hijacking, this tactic relies on social engineering to fool mobile carriers into transferring a user’s number to a new SIM card. Bad actors often conduct research on their targets—and gather personal information available on the internet from phishing, the dark web, or information contained across the internet or social media—in order to impersonate them. The hacker poses as the victim to the carrier, claiming a phone was lost or upgraded.

Learn how to recognize and defend against these tactics in our guide to avoiding social engineering attacks.

When an attacker successfully tricks the carrier, the attacker gets a new SIM connected to your number—and you lose control of your number and your associated sensitive accounts. They can receive all verification codes, phone calls, and texts meant for you. This allows them to reset passwords, lock you out of your accounts, and impersonate you for follow-on attacks in your network.

2. SIM Cloning

SIM cloning involves copying the contents of your SIM card onto a blank one using specialized hardware. Unlike SIM swapping, cloning requires physical access to your device, even if only for a few minutes.

Once cloned, attackers can place the duplicate SIM into another phone, gain control of your SIM, and receive all the same communication. While less common than swapping, this method is still dangerous—especially during targeted attacks or corporate espionage.

3. Simjacker

Simjacker is a vulnerability in older SIM cards that allows attackers to abuse the S@T Browser, a legacy application in many SIM Toolkits. The attacker uses the flaw to send hidden SMS messages that contain SIM toolkit commands. Once received, they can remotely track your location data, monitor texts, and potentially install more malware.

Over a billion SIM cards are vulnerable to Simjacker attacks, especially in countries with older mobile infrastructure, according to AdaptiveMobile, which uncovered the issue.

How to Know If Your SIM Card Is Hacked

SIM card breaches often go unnoticed—until it’s too late. Attackers often take over SIM cards stealthily, without alerting victims. Watch for these red flags:

• You’re locked out of accounts that require SMS verification. (Attackers may have already hijacked your SIM card, received verification messages, and changed passwords.)
• You can’t send or receive phone calls or messages.
• You’re prompted to restart your phone without cause
• You notice charges or data usage on your cell phone bill you didn’t make
• You receive alerts from unfamiliar apps or devices
• Your phone’s GPS location shows a different region

A hacked SIM card is often a precursor to a larger data breach. Acting quickly can limit the impact.

What Hackers Can Access with a Compromised SIM

Once attackers have hacked a SIM card, they can take control of a range of sensitive data:

• Banking apps
• Cloud storage platforms
• Email and enterprise systems
• Social media accounts
• Health portals containing PHI and medical information

Attackers can also use compromised devices to pivot into corporate environments, especially if the victim is linked to third-party vendors or business associates.

How to Protect Yourself From SIM Card Exploits

You don’t have to be a cybersecurity expert to guard against SIM card attacks. These simple actions make a big difference:

• Avoid sharing your mobile number online unnecessarily
• Use app-based authentication (e.g., Google Authenticator) instead of SMS codes
• Set up a SIM PIN or passcode through your mobile provider
• Watch out for phishing links and suspicious emails
• Don’t respond to texts from unknown numbers
• Monitor your phone bill and device activity regularly

For enterprises, it’s critical to secure both corporate and personal devices that access internal systems or third-party partner environments. A single compromised phone can become the weak link in a broader vendor cybersecurity scenario.

What to Do If You’ve Been Hacked

If you believe your SIM card has been compromised:

• Contact your carrier immediately to freeze or deactivate the compromised number (some carriers have web pages that provide instructions on how to safely contact them in cases of SIM hacking)
• Reset passwords for accounts—and especially for sensitive accounts such as email, banking, and cloud apps
• Enable fraud alerts on your credit accounts
• Notify law enforcement or your cybersecurity team
• Scan your device for additional malware or spyware infections
• Review recent logins and revoke access to suspicious devices

Real-World Impact of SIM Hacks

One of the most striking examples of a SIM swap attack against the U.S. Securities and Exchange Commission (SEC) that occurred in  2024. An attacker convinced a mobile carrier to transfer the phone number linked to the agency’s Twitter account to a new device. With control of the number, the attacker bypassed authentication and reset the account password—seizing control of the SEC’s online presence.

These types of incidents highlight why threat intelligence and continuous monitoring matter.

It’s not just about preventing theft—it’s about protecting trust and access to critical systems. 

Go Deeper

SIM hijacks exploit trust in outdated authentication methods. Learn how adopting a Zero Trust security model can help your organization reduce risk, limit lateral movement, and better secure sensitive data at every access point.

Why SecurityScorecard Is Your Partner in Supply Chain Cybersecurity

At SecurityScorecard, we help businesses identify and respond to risks across their entire vendor ecosystem through:

• Continuous monitoring of your supply chain
• Actionable insights into vulnerabilities before attackers exploit them
• Supply Chain Detection and Response (SCDR) capabilities that go beyond basic risk scoring

Whether you’re managing third-party risk, aligning with governance, risk, and compliance (GRC) frameworks, or protecting against identity-based exploits like SIM swaps, SecurityScorecard empowers you with visibility and control.

Our Global Third-Party Breach Report shows how these risks continue to grow across complex vendor ecosystems.