
Clicking on the file contained inside the ZIP attachment infects users with the Troj/Agent-FZB Trojan horse, which drops two rootkits in an aim to hide from filtering.
Hackers use rootkit technology to maintain access to a compromised computer without the user's knowledge, according to Graham Cluley, senior technology consultant at Sophos.
"If you receive an unsolicited email with an encouragement to run the 'cool screensaver' attached then alarm bells should instantly be ringing in your head," said Cluley.
Sophos recommends companies automatically update their corporate virus protection and run a consolidated solution to defend against malware, spyware, hackers and spam.