Trojan horse
Trojan horse
A Trojan horse is an email virus usually released by an email attachment. If opened, it will scour your hard drive for any personal and financial information such as your social security, account, and PIN numbers. Once it has collected your info, it is sent to a thief’s database.
you can find more information about them with this website
http://antivirus.about.com/b/2006/05/31/whats-a-trojan-horse-virus.htm