This popular and well-engineered suite by Dug Song includes many tools: dsniff, filesnarf, mailsnarf, msgsnarf, urlsnarf, and webspy passively monitor a network for interesting data (passwords, e-mail, files, etc.); arpspoof, dnsspoof, and macof facilitate the interception of network traffic normally unavailable to an attacker (e.g, due to layer-2 switching); and sshmitm and webmitm implement active monkey-in-the-middle attacks against redirected ssh and https sessions by exploiting weak bindings in ad-hoc PKI. A separately maintained partial Windows port is available here. The suite suffers from the lack of any updates in the last decade, but it is still a great toolset for handling your password sniffing needs.
For downloads and more information,
visit the dsniff homepage.
I know that the dsniff package isnt itself a virus, but if you download it (im not aware of apt-get or wget/curl) your anti virus may think its a virus. Anti virus uses hashes to find malicous code, and since dsniff most likely does some funny behind the scenes port sniffing/configuration your antivirus may think its a virus. I would recommend finding the hashes in sha256 and checking yourself for the package confidentiality. Dsniff is a nice tool to use, havong several good features.