How about that -- a benign (?) protective virus:
An old virus affecting routers and other devices running Linux appears to be acting as a digital vigilante, protecting routers in the dark alleyways of the Internet from other malware infections.
The difference, according to Symantec researcher Mario Ballano, is that Wifatch seems only to be defending, not attacking. "It appeared like the author was trying to secure infected devices instead of using them for malicious activities," he wrote in a blog post Thursday.
A further sign of its author's good intentions, Ballano said, is that there is no attempt to hide the malware: the code is not obfuscated, and it even includes debug messages making it easier to analyze.