ET MALWARE DOUBLEBACK CnC Activity

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE DOUBLEBACK CnC Activity";
    flow:established,to_server;
    http.method;
    content:"POST";
    http.uri;
    content:"/admin"; startswith;
    content:"/client.php"; within:13; endswith; fast_pattern;
    pcre:"/^\/admin(?:[0-9]{1,2})?\/client\.php$/";
    http.header_names;
    content:!"|0d 0a|Referer|0d 0a|";
    http.content_type;
    content:"multipart/form-data"; bsize:19;
    reference:url,twitter.com/k3dg3/status/1532454383631450115;
    reference:url,www.mandiant.com/resources/unc2529-triple-double-trifecta-phishing-campaign;
    classtype:command-and-control;
    sid:2036823; rev:2;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2022_06_03, deployment Perimeter, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_01_20;
)