alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE JS/Unk Downloader 0 Byte POST CnC Checkin"; flow:established,to_server; http.method; content:"POST"; http.header; content:"Content-Length|3a 20|0|0d|"; http.user_agent; content:"xmsSofts_1.0.0_"; depth:15; fast_pattern; content:"|5c|"; endswith; http.header_names; content:!"Referer"; classtype:command-and-control; sid:2026760; rev:4; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_01_07, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag Downloader, tag JavaScript, updated_at 2022_03_24;)