alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET RETIRED Confucious APT CnC Checkin"; flow:established,to_server; content:"XOXO"; content:"XOXO"; distance:0; within:50; pcre:"/^(?:[A-F0-9]{2}-){5}[A-F0-9]{2}/R"; content:"XOXO|20|Host|20|Name|3a|"; fast_pattern; reference:md5,23537d81e9cd285b41185a0e4c3d37c1; classtype:trojan-activity; sid:2041928; rev:2; metadata:attack_target Client_Endpoint, created_at 2022_12_06, deployment Perimeter, former_category MALWARE, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_09_23, reviewed_at 2024_09_23;)