A Symantec researcher has discovered a worm that runs on embedded Linux systems, like those found in set-top boxes and routers. It's common for owners of these devices to forget about them, letting them run in the background for so long as they don't misbehave -- and as a result, they are often out of date. The worm, called Linux.Darlloz, attacks out-of-date Linux installations running on Intel hardware (a small minority in the embedded systems world), but it would not be hard to modify it to attack embedded linuces on other chips.
In addition to being out-of-date, many of these systems have "forever day" bugs that will never be patched by their vendors, making them especially hard to secure. The anonymously authored "Internet Census 2012: Port scanning /0 using insecure embedded devices" showed that a dedicated attacker could compromise well over a million devices without much work, recruiting them to run unprecedented denial of service attacks (I wonder if anyone's thought of using this method for mining Bitcoins?).
As the researcher Ang Cui has demonstrated, embedded systems attacks are especially pernicious because it's difficult to boot them from known-good sources. Once an attacker compromises your router, printer, or set-top box, she can reprogram it to give the appearance of accepting updates without actually installing them, meaning that the system can never be provably restored to your control.
The details of the Linux.Darlloz show a much more primitive and unambitious attack, but it hints at a pretty frightening future for the compromised Internet-of-Things (I wrote a short story about this, called "The Brave Little Toaster").
"Upon execution, the worm generates IP addresses randomly, accesses a specific path on the machine with well-known ID and passwords, and sends HTTP POST requests, which exploit the vulnerability," Hayashi explained. "If the target is unpatched, it downloads the worm from a malicious server and starts searching for its next target. Currently, the worm seems to infect only Intel x86 systems, because the downloaded URL in the exploit code is hard-coded to the ELF binary for Intel architectures."
The researcher went on to say the attacker behind the Intel version is also hosting ELF files that exploit the other chip architectures. The “e_machine” value in ELF header indicates that the worm is for ARM architecture.
While not posing much of a real-world threat now, Darlloz demonstrates a major shortcoming with most Internet-of-things devices available today—they typically run Linux or other types of open source code that are woefully out of date. Making matters worse, many Internet-connected consumer devices can't be updated because their lightweight hardware can't handle the requirements of newer code versions. Hijacking one of these devices thus becomes much easier than exploiting, say, an up-to-date version of Windows, OS X, or Linux.
New Linux worm targets routers, cameras, “Internet of things” devices [Dan Goodin/Ars Technica]