Tor Project flags Russian 'exit node' server for delivering malware

He suspected attackers were "patching" binaries during man-in-the-middle attacks and took a look at more than 1,110 Tor exit nodes.

Pitts only found one Tor exit node that was patching binaries. The node would modify only uncompressed portable executables, he wrote.

"This does not mean that other nodes on the Tor network are not patching binaries; I may not have caught them, or they may be waiting to patch only a small set of binaries," he wrote.

The broad lesson for users is that they should be wary of downloading code that is not protected by SSL/TLS, even if the binary itself is digitally signed, Pitts wrote.

"All people, but especially those in countries hostile to 'Internet freedom,' as well as those using Tor anywhere, should be wary of downloading binaries hosted in the clear -- and all users should have a way of checking hashes and signatures out of band prior to executing the binary," he wrote.