Trojans are malicious applications that pose themselves as legitimate software in order to trick users to install them. Once on the victim's machine, it may run any number of malicious process to steal vital information or inflict damage to other software.
Some variants seem to be related to Webrebates.
Agent.b is a Trojan backdoor that opens the infected machine to remote access.Agent.b is packed with two packers: Morphine and UPX. The packed file size is 38 KB and unpacked - 104 KB. Agent.b is controlled over IRC channels. The controller can download and execute files on the infected machine.