Infostealer is a detection name used by Symantec to identify malicious software programs that gathers confidential information from the compromised computer. It is is a type of Trojan horse program that has a very specific payload goal.
This Trojan gathers confidential information from the computer and sends it to a predetermined location. This information can be financial, related to the compromised computer or user credentials for various web sites. Often the Trojan may steal a combination of all three types of sensitive information.