alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Unk Downloader CnC Activity"; flow:established,to_server; http.request_line; content:"GET /"; startswith; content:"image.php?id="; fast_pattern; pcre:"/^[0-9A-F]{21,22}\x20HTTP\/1\.1$/R"; http.content_type; content:"application/x-www-form-urlencoded"; bsize:33; http.header_names; content:!"|0d 0a|Referer|0d 0a|"; content:!"|0d 0a|User-Agent|0d 0a|"; reference:md5,1743533d63a8ba25142ffa3efc59b50b; classtype:command-and-control; sid:2032342; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_03_29, deployment Perimeter, deployment SSLDecrypt, performance_impact Low, confidence High, signature_severity Major, updated_at 2021_04_19;)