Rule Search, Criteria (Alert) Tab

Allows you to specify criteria of the alerts generated by the rules for which you are searching. The fields are defined as follows:

Alert source
Allows you to specify the source of the alert generated by the rule, or to identify it using wild card characters or text strings within the name. Alert source is typically defined by the creator of the rule.
Alert severity
Allows you to specify the severity of the alert generated by the rules for which you are searching, such as Security Breach or Critical Error.