alert tcp $HOME_NET any <> $EXTERNAL_NET any (msg:"ET RETIRED Yahoo IM message"; flow:established; content:"YMSG"; depth:4; classtype:policy-violation; sid:2001260; rev:7; metadata:created_at 2010_07_30, former_category CHAT, confidence Medium, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2026_08_28;)