alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET RETIRED Yahoo IM Client Install"; flow:established,to_server; http.uri; content:"/ycontent/stats.php?version="; nocase; content:"EVENT=InstallBegin"; nocase; classtype:policy-violation; sid:2002659; rev:10; 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;)