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.
Comment:
Implements a PPTP challenge/response sniffer. These c/r can be input into L0phtcrack to obtain the password, and an active attack on PPTP logons via the MS-CHAP vulnerability to obtain the users password hashes.