[1llusion]

Wait... are you talking about spreading via USB flash drive? That is quite common (Used to be via autorun.inf, now they use exploits like the LNK exploit). Or a hardware keylogger? (they exist too, you plug them between the keyboard and the computer and they monitor every key. No installation required, undetectable by antiviruses and work on any OS).

EDIT: just found the LNK exploit (http://www.exploit-db.com/exploits/16574/). I might do a little tutorial on it on my blog