In late December 2009, a new Firmware will be released for the SA500 series router which will allow the loading of a Cisco IPS signature file.
Intrusion Prevention System (IPS) signatures are in the form of "S-files", which are lists of signatures and their characteristics.
The activation of the IPS will required a license SKU be purchased for the product:
eDelivery IPS for SA 500 Series License L-SA500-IPS-1YR=
This is defined in the product datasheet:
IPS Signatures are sorted by Signature ID in the following link. Signature name and signature engine information are also listed.