By Seth Fitzgerald / CIO Today. Updated July 22, 2013.
A German security researcher has found a major flaw in the type of encryption that many cell phone SIM cards use.
According to researcher Karsten Nohl, the DES (data encryption standard) protocol which has been around since the 1970s is weak against attacks, despite it still being used on half of all SIM cards.
Nohl, who will be presenting his findings at the Black Hat security conference in Las Vegas next week, tested 1,000 SIM cards over a two-year period and has come to the conclusion that as many as 750 million cell phones globally could be vulnerable to these relatively easy attacks.
The two largest carriers in the U.S., Verizon and AT&T, both reportedly have said they have moved away from DES encryption and their SIM cards are not vulnerable to the flaw.
By looking at the security features present on the test phones, he discovered that in a quarter of them that use the older encryption standard, a hacker could exploit carrier text messages. Cell phone carriers frequently send out text messages to phones, and Nohl was able to trick devices into seeing him as a carrier. After doing so, the phone accepted a text message and replied with the SIM card's 56-digit key.
Once hackers have access to a SIM card's unique key, they are able to take over the device. Nohl said hackers with a SIM key are able to do practically anything they want with the phone.
"We can remotely install software on a handset that operates completely independently from your phone," Nohl said. "We can spy on you. We know your encryption keys for calls. We can read your SMS's. More than just spying, we can steal data from the SIM card, your mobile identity, and charge to your account."
Even though a large portion of the phones that Nohl tested did not accept the message pretending to be from the carrier, many of them did, and in doing so the phone frequently provided a cryptographic signature. The issue with the signatures used by the SIM cards is that Nohl was able to crack them in under a minute.
Breaking the encryption key gave Nohl access to the phone, allowing him to download a virus onto the SIM card that would eavesdrop on calls, collect data, and send messages or calls.
Fixing the Vulnerability
Nohl has yet to release the specifics of his research to the public but he has already notified the GSM Association about his findings. The International Telecommunications Union, a sub-group of the United Nations, said the research was "hugely significant."
Wireless telecom analyst Jeff Kagan said most people do not add virus protection to their cell phones, and when combined with weak encryption security, phones are vulnerable devices.
When it comes to fixing the problem, which potentially affects more than 750 million devices, Kagan said there were a few things that must be done.
"The solution has to come from many areas," Kagan told us. "One is to continually upgrade SIM cards. Two is to have security protection on the networks, which we do have. Three is to personally protect our devices with protection software like we do on our computers."