alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET RETIRED Yahoo IM conference invitation"; flow:established,to_client; content:"YMSG"; nocase; depth:4; content:"|00 18|"; offset:10; depth:2; classtype:policy-violation; sid:2001256; 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;)