The direction of the signature varies from one application toanother. It's all up to the behavior. For signatures detecting IM'sbehaviors such as File Transfer, Chat, Online Game, AudioCommunication, and Video Communication, the directions arebi-directional. This means that DFL-M510 can detect such attemptseither from LAN to WAN or from WAN to LAN.
For signatures detecting HTTP download attempts, IM loginattempts, Web Mail controls (Yahoo Mail, Gmail, and Hotmail), WebUpload, Web Download, and Java Applet download attempts, thedirections are unidirectional.
For signatures detecting malicious traffic made by worm/Trojan,the direction is bi-directional.