alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Suspected TA451 Related FalseFont Backdoor Activity M2"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/realtime/negotiate?negotiateVersion="; startswith; fast_pattern; content:!"|2e|"; threshold:type limit, count 1, seconds 300, track by_src; reference:md5,5b759c6db78de7587a9d201e8ea28c03; reference:md5,6fd5d31d607a212c6f7651c79e7655a3; reference:url,twitter.com/MsftSecIntel/status/1737895717870440609; classtype:trojan-activity; sid:2049948; rev:3; metadata:attack_target Client_Endpoint, created_at 2024_01_09, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_02_05, reviewed_at 2024_04_05; target:src_ip;)