Seems to be similar to the attack in this topic.
http://forum.avast.com/index.php?topic=27671.0
If you click on links in e-mails, you’re always likely to be taken to a site using the latest exploits to install malware, and the malware itself is very likely to be a variant undetected by most AV’s, because new variants are churned out every hour.
Starting with Agent-a to Agent-z, that’s 26 variants. Agent-aa is number 27 and Agent-zz is number 676. Adding a third letter goes up to 17576 varaints.
With so many new variants emerging, no AV will catch all of them.
If you still have a copy of the file, submit it to VirusTotal to compare AV performance.
