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.
Win32.Agent.dn is a IRC backdoor Trojan , which runs continuously in the backdrop, providing a backdoor server on port 6667. It connects to an Internet Relay Chat (IRC) server and joins a specific channel, where it listens for instructions. The supposed instructions are implemented locally on affected machines.
Large amount of Hijacked domains are placed in the Hosts file. Its probably better to delete the file itself than to fix each item.(and create a Backup)
File location is C:\Windows\System32\drivers\etc\hosts