alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET CHAT IRC authorization message"; flow:established; content:"NOTICE AUTH"; content:"Looking up your hostname..."; nocase; classtype:misc-activity; sid:2000355; rev:5; metadata:created_at 2010_07_30, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2019_07_26;)