alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32/Echmark/MarkiRAT CnC Activity M3"; flow:established,to_server; http.method; content:"POST"; http.uri; content:".php?u="; http.user_agent; content:"WinHTTP"; bsize:7; http.request_body; content:"p=<br><mark>Hello|3a 20|"; startswith; fast_pattern; http.header_names; content:!"Referer"; reference:md5,1fe34d84a058156296e86888ddd5cac9; reference:url,securelist.com/ferocious-kitten-6-years-of-covert-surveillance-in-iran/102806/; classtype:command-and-control; sid:2033429; rev:1; metadata:attack_target Client_Endpoint, created_at 2021_07_26, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_07_26;)