A critical vulnerability in trendy web programming kit Ruby on Rails is being abused to conscript hacked website servers into a growing botnet army.
A security bug (CVE-2013-0156) in the open-source application framework was patched in January, but months later many website owners have failed to apply the update, leaving code on numerous sites vulnerable.
Shortcomings in Ruby on Rails' parameter-parsing code allows miscreants to bypass authentication systems, inject and execute arbitrary code, or perform a denial-of-service attack on a Rails application, an advisory by US CERT explains.
The bug can be exploited to force a vulnerable server to download, compile and run some C code that takes control of the machine. Once compromised, the web server becomes a remotely controlled drone in a network of zombie computers, which blindly obey commands issued from afar by crooks in an IRC chatroom. These orders could be to send out spam, pummel a target on the internet in a distributed denial-of-service (DDoS) attack, or similar.
Martijn Grooten, anti-spam test director at Virus Bulletin, noted that the communications channel used to send instructions to the zombie bots is unencrypted, and therefore open to hijacking by any cyber-crim. Although perhaps basic in its design, the botnet is a powerful resource for various potential forms of cybercrime.
Ruby on Rails is knocked by some security experts - such as Gunter Ollmann, CTO of IOActive - as a development platform that's unfit for production servers. Nonetheless the technology is widely deployed. Those that do use it are advised to update their systems to versions 3.2.11, 3.1.10, 3.0.19 or 2.3.15.
The creation of the Ruby on Rails botnet was first identified by security researcher Jeff Jarmoc of Matasano Security. "This is a pretty straightforward skiddy exploit of a vulnerability that has been publicly known, and warned about, for months," Jarmoc concluded in a post on his personal blog.
Cybercrooks are increasingly looking towards exploiting vulnerable software on web servers, rather than less powerful client PCs, in order to create stronger zombie networks. For example, compromised WordPress installations have recently been abused to create a botnet linked to recent DDoS attacks. Web servers invariably have much higher capacity internet connections than home PCs, making them eminently suitable as a platform for overloading targeted websites with junk traffic. ®