Embedded Malware - An Analysis of the Chuck Norris Botnet

Abstract

This paper describes a new botnet that we have discovered at the beginning of December 2009. Our Net Flow-based network monitoring system reported an increasing amount of Telnet scanning probes. Tracing back to a source we have identified world wide infected DSL modems and home routers. Nowadays, various vendors use Linux in this kind of devices. A further investigation has shown that most of deployed SoHo (small office/home office) devices use default passwords or an unpatched vulnerable firmware. Some devices allow a remote access via Telnet, SSH or a web interface. Linux malware exploiting weak passwords allows fast propagation and a virtually unlimited potential for malicious activities. In comparison to a traditional desktop oriented malware, end users have almost no chance to discover a bot infection. We call the botnet after Chuck Norris because an early version included the string [R]anger Killato : in nome di Chuck Norris!