Passive monitors and other monitors that provide pattern checking enable you to apply simple regular expression syntax.
You can use a rule expression to test a string or a page of text for pattern matching. You can check for word frequency, HTTP error pages, literal strings, and much more.
After creating and testing the expression, click OK to insert the string into the Match on box.
Note: If you have multiple payload "match on" expressions, they are linked by "OR" logic - not "AND" logic. Example: If you have two expressions, one set to "AB" and the other to "BA", it will match against a trap containing any of the following: "AB" or "BA" or "ABBA".