Trend Micro Viruswall on Linux Firewall

Hi All,
After installing and configuring Trend Micro’s Viruswall for Linux Red Hat 6.2(ScanEngine 5.3, Pattern File 873) just last week, I did a test by sending the machine the Anna Kournikova virus from a remote location. It did not detect a virus. When I sent it the Hybris worm, it did detect a virus.
Does anybody know why this could be? Even with the latest update, it’s letting Anna pass. Trend Micro couldn’t help me so far.

Thank you! Liza