And Now A Malware Tool That Has Your Back

Security researchers at Symantec have been tracking a malware tool that, for a change, most victims wouldn’t actually mind have infecting their systems--or almost, anyway.

The threat dubbed Linux.Wifatch compromises home routers and other Internet-connected consumer devices. But unlike other malware, this one does not steal data, snoop silently on victims, or engage in other similar malicious activity.

Instead, the author or authors of the malware appear to be using it to actually secure infected devices. Symanetc believes the malware has infected tens of thousands of routers and other IoT systems around the world. Yet, in the two months that the security vendor has been tracking Linux.Wifatch it has not seen the malware tool being used maliciously even once.

“In fact all the hardcoded routines seem to have been implemented in order to harden compromised devices,” Symantec security researcher Mario Ballano wrote in a blog post published Thursday.

Wifatch has one module that attempts to detect and remediate any other malware infections that might be present on a device that it has infected. “Some of the threats it tries to remove are well known families of malware targeting embedded devices,” Ballano wrote.

Another module appears designed specifically to protect Dahua DVR and CCTV systems. The module allows Wifatch to set the configuration of the device so as to cause it to reboot every week, presumably as a way to get rid of any malware that might be present or running on the system.

Most Wifatch infections that Symantec has observed have been over Telnet connections to IoT devices with weak credentials, according to the vendor.

In keeping with its vigilante role, once Wifatch infects a device it tries to prevent other malicious attackers from doing the same by shutting down the Telnet service. It also connects to a peer-to-peer network to receive periodic updates.

Wifatch even leaves a message for device owners asking them to upgrade their device firmware and to change their passwords, Ballano said. “Telnet has been closed to avoid further infection of this device,” the Wifatch message, posted on the Symantec blog, notes. “Please disable telnet, change telnet passwords, and/or update the firmware.”

Wifatch is mostly written in Perl and targets IoT devices based on ARM, MIPS and SH4 architectures. The hitherto white hat malware tool ships with a separate static Perl interpreter for each targeted architecture. The code itself is not obfuscated like many malware tools are these days. In fact it contains several debug messages that actually enable easier code analysis.

“It looks like the author wasn’t particularly worried about others being able to inspect the code,” Ballano wrote.

For all its unusually good behavior, Wifatch should still be treated as malware, according to the researcher. Like other malware, Wifatch still is a piece of code that infects devices without any user consent. It also contains several general-purpose backdoors that can be exploited for malicious use at a future date.

However, the use of the backdoors is cryptographically protected to ensure that only the malware’s real authors can use them, Ballano added.

“Whether the author’s intentions are to use their creation for the good of other IoT users—vigilante style—or whether their intentions are more malicious remains to be seen,” the researcher said.

Router infections can be hard for end users to detect. However, it is possible to get rid of Wifatch on an infected device simply by rebooting it. Users should also consider updating their device software and changing default passwords on home routers and IoT devices, Ballano said.