ET MALWARE FormBook CnC Checkin (POST) M2

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE FormBook CnC Checkin (POST) M2";
    flow:established,to_server;
    http.method;
    content:"POST";
    http.uri;
    content:!".";
    content:!"?";
    content:!"&";
    http.request_body;
    content:"="; within:15;
    content:"|00 00 00 00 00 00|"; fast_pattern;
    isdataat:!1,relative;
    pcre:"/=[a-z0-9\(_~\-\.\x00]{300,}\x00$/i";
    http.accept_enc;
    content:"gzip, deflate"; depth:13; endswith;
    http.connection;
    content:"close"; depth:5; endswith;
    http.content_len;
    byte_test:0,>,300,0,string,dec;
    http.header_names;
    content:"|0d 0a|Host|0d 0a|Connection|0d 0a|Content-Length|0d 0a|"; depth:36;
    reference:md5,6f5d2b42f4a74886ac3284fa9a414a87;
    classtype:command-and-control;
    sid:2031413; rev:2;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2020_12_16, deployment Perimeter, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_12_16;
)