New attack puts routers, cell phones at risk

A security researcher has found a way to use the common 'null pointer' error to deliver malicious code via a router or mobile device

A security researcher at Juniper Networks has developed a new form of attack that can be used to run unauthorized software on a wide range of computing devices, including routers and mobile phones.

In a demonstration set to take place at the CanSecWest security conference in Vancouver Thursday, Juniper's Barnaby Jack says he will show how this technique could be used to take control of a router and then inject malicious software on virtually every machine on the network.

Jack says he has discovered a way to turn a common type of computing error -- called a null pointer dereferencing error -- into something far more dangerous than previously thought. Researchers have known for years how to create these flaws, which occur when the computer tells a program that the part of memory that it's looking for is invalid, or "null."

Until now, null pointer errors had not been considered particularly devastating. They typically cause the affected computer to crash but cause no more serious damage.

On Thursday, however, Jack will show how these flaws can be used to run unauthorized software on certain types of devices. This new technique, is "100 percent reliable, and it results in code execution on the device," he said.

Jack's null pointer exploit is effective on the Arm and xScale processors that are widely used in embedded devices, but it does not work on Intel architecture processors used by PCs.

In his demonstration, Jack plans to show how his attack could be used to make changes to the firmware of a router so that it injects a malicious code into any executable files downloaded from the Internet. This technique could be used to turn legitimate software updates -- Microsoft's monthly software patches, for example -- into an avenue of attack.

Jack bills his technique as a more reliable alternative to hacker techniques like buffer overflow attacks, which attempt to trick the processor into running code that is sneaked into the computer's memory.

If Jack's claims prove to be accurate, this attack will certainly come as a surprise to the companies that use Arm and xScale processors in their devices, said Russ Cooper, a senior information security analyst at Cybertrust. "The Arm processor is supposed to be a secure environment, so that this flaw exists represents a bigger problem."

The discovery would be much more significant, however, if it worked on the x86 processors used by most PCs, he added.

Chip makers could correct the problem in future systems by making a simple change to the processor, but systems that have already shipped are vulnerable to the attack, Jack said.

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