New SIM Card Flaw Lets Hackers Hijack Any Phone Just By Sending SMS

Cybersecurity researchers today revealed the existence of a new and previously undetected critical vulnerability in SIM cards that could allow remote attackers to compromise targeted mobile phones and spy on victims just by sending an SMS.

Dubbed “SimJacker,” the vulnerability resides in a particular piece of software, called the S@T Browser (a dynamic SIM toolkit), embedded on most SIM cards that is widely being used by mobile operators in at least 30 countries and can be exploited regardless of which handsets victims are using.

What’s worrisome? A specific private company that works with governments is actively exploiting the SimJacker vulnerability from at least the last two years to conduct targeted surveillance on mobile phone users across several countries.

S@T Browser, short for SIMalliance Toolbox Browser, is an application that comes installed on a variety of SIM cards, including eSIM, as part of SIM Tool Kit (STK) and has been designed to let mobile carriers provide some basic services, subscriptions, and value-added services over-the-air to their customers.

Since S@T Browser contains a series of STK instructions—such as send short message, setup call, launch browser, provide local data, run at command, and send data—that can be triggered just by sending an SMS to a device, the software offers an execution environment to run malicious commands on mobile phones as well.

How Does Simjacker Vulnerability Work?

Disclosed by researchers at AdaptiveMobile Security in new research published today, the vulnerability can be exploited using a $10 GSM modem to perform several tasks, listed below, on a targeted device just by sending an SMS containing a specific type of spyware-like code.

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The SIMalliance has acknowledged the issue and provided recommendations for SIM card manufacturers to implement security for S@T push messages.