We’re familiar with Trojan Horses , but there are other threats out there in the dark corners of the internet that you should be aware of…
Downloader—A program that retrieves and installs additional files when run. Most are set up to retrieve from a designated web or FTP site.
Proxy—An infected computer can become a front for a hacker’s, allowing the fiend to do their bidding with you taking the blame. As attack tools, SMTP and FTP proxies are often used in conjunction with Firewall Killers, Downloaders, and Trojan Horses.
Dropper—When this kind of program runs it installs a worm , or virus  onto the hard drive. It is not a virus, just a carrier of malicious code that drops a virus onto the system. Antivirus scans cannot detect these.
Hopefully you won’t be bitten by any of these beasts.
David Samuel Thomas