Summary
Your system seems to be infected by the Bugbear.B virus (its backdoor has been detected on port 81).
More information: http://www.f-secure.com/v-descs/bugbear_b.shtml
Solution
Use your favorite antivirus to disinfect your
system. Standalone disinfection tools also exist :
ftp://ftp.f-secure.com/anti-virus/tools/f-bugbr.zip
