Linux Worm Targets Embedded Devices

As security researchers look into a Linux worm that's gaining steam by targeting embedded devices, the lessons they learn could prove instructive for the industry as it seeks to protect the Internet of Things.

First brought to the forefront by researchers with Symantec just before Thanksgiving, and subsequently studied by others in labs at DeepEnd Research and Cisco, the Zollard worm has spiked the number of PHP exploit attempts for devices like routers, set-top boxes, security cameras, and more. The worm takes advantage of an old PHP vulnerability patched in May 2012 that, according to Cisco, is heavily exploited by a number of worms.

In the case of Zollard, in particular, the malware is tuned to go after a number of different architecture types beyond x86, including ARM, PPC, MIPS, and MIPSel. This activity of exploiting vulnerabilities in embedded devices could prove a more visceral portend for the potential dangers posed by the Internet of Things that many security pros have already been warning about for the past few years.

[Are you using your human sensors? See Using The Human Perimeter To Detect Outside Attacks.]

"The Internet of Things is a really terrible term to describe all of the terrible embedded devices that we have all around us that no one is going to ever fix and which will eventually be our downfall," says HD Moore, chief research officer at Rapid7. "I'm a little biased because I've spent so much time on it, but embedded devices are getting compromised left and right."

The big danger of these devices is the combination of forgetability and the hidden compute power they hold -- they're often single-purpose but still built on something like a Linux platform with online connectivity.

"They're small enough that a lot of administrators forget they're there and forget to patch them, change default passwords, and things like that," says Spencer McIntyre, security researcher for SecureState. "But they're running software that is well-known enough to contain vulnerabilities that can be leveraged by attackers."

And enterprises can't afford to sniff at the Internet of Things as a consumer trend only affecting newly connected house appliances; embedded devices are all over the enterprise, with plenty of items such as conference-room devices and printers at risk to malware like Zollard if they're not protected. In particular, routers and switches at large organizations could prove a juicy target for attackers, McIntyre says. "If someone is able to compromise a critical piece of infrastructure like that, then the floodgates are really open for what that attacker can do," McIntyre says, emphasizing the importance of organizations to re-evaluate their patch management and configuration management routines for these forgotten devices.

Unfortunately, embedded devices are often left to linger without appropriate firmware updates ever applied and with configuration frequently left at default states after a set-it-and-forget-it installation.

"This results in most embedded devices running fairly standard configurations," wrote Craig Williams, security researcher for Cisco. "If a vulnerability is found in default or common embedded configurations, attackers are much more likely to focus on it since the attack surface is going to be widespread."

Williams agreed that this stability could make attacks like Zollard more prevalent as these devices are "co-opted" by attackers for launching malware, reconnaissance, and other malicious activity. Moore, for example, predicts that we'll increasingly see botnets made up of infected embedded systems.

According to Williams, the answer is protection at the network level, pointing to current IDS signatures that block attacks against the PHP vulnerability that Zollard attacks.

"Though, as always, practicing defense in depth where possible is even better," he says.

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