alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE UsefulTyphon CnC Activity M2"; flow:established,to_server; http.method; content:"GET"; http.uri; content:".down"; fast_pattern; pcre:"/\/[a-f0-9]{16}\.down$/"; http.header_names; content:!"Referer"; reference:md5,768c84100d6e3181a26fa50261129287; classtype:command-and-control; sid:2036503; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2020_10_06, deployment Perimeter, malware_family Kimsuky, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_06;)