Fivesec is a trojan that turns the compromised computer into a spam relay. Once executed, the parasite secretly installs itself to the system. It injects malicious code into legitimate processes in order to hide its presence and activity. Then the trojan downloads available updates and the list of spam recipients. After a while, Fivesec starts sending out spam e-mails from the compromised computer using own mail engine. The parasite is able to bypass the Windows Firewall. It runs on every Windows startup.