alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE W32/Echmark/MarkiRAT CnC Request"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/echo.php?req="; fast_pattern; content:"&u="; distance:0; content:"_"; distance:0; http.user_agent; content:"Microsoft WinHttp"; depth:17; endswith; reference:md5,d22d9ce61e6aea72aa9a8a233530db43; reference:url,securelist.com/ferocious-kitten-6-years-of-covert-surveillance-in-iran/102806/; classtype:trojan-activity; sid:2033401; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2020_07_06, deployment Perimeter, deployment SSLDecrypt, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_07_06;)