alert tcp $EXTERNAL_NET 25 -> $HOME_NET any (msg:"ET HUNTING Suspicious SMTP handshake reply"; flow:established,to_client; content:"701 IMHERE"; depth:10; classtype:unknown; sid:2008563; rev:4; metadata:created_at 2010_07_30, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_03_06;)