ET MALWARE FormBook CnC Checkin (GET) M5

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE FormBook CnC Checkin (GET) M5";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/?"; offset:3;
    pcre:"/^[A-Za-z0-9_\-]{1,15}=(?:[A-Za-z0-9_\-]{1,25}|(?:[A-Za-z0-9\+\/]{4})*(?:[A-Za-z0-9\+\/]{2}==|[A-Za-z0-9\+\/]{3}=|[A-Za-z0-9\+\/]{4}))&[A-Za-z0-9_\-]{1,15}=(?:[A-Za-z0-9_\-]{1,25}|(?:[A-Za-z0-9\+\/]{4})*(?:[A-Za-z0-9\+\/]{2}==|[A-Za-z0-9\+\/]{3}=|[A-Za-z0-9\+\/]{4}))(?:&sql=\d*)?$/R";
    http.connection;
    content:"close"; bsize:5;
    http.header_names;
    content:!"Referer";
    content:"|0d 0a|Host|0d 0a|Connection|0d 0a|User-Agent|0d 0a 0d 0a|"; fast_pattern;
    reference:md5,04777e7ab425b2d82227945f81d2c1f8;
    classtype:command-and-control;
    sid:2050745; rev:2;
    metadata:attack_target Client_Endpoint, created_at 2024_02_07, deployment Perimeter, malware_family Formbook, performance_impact Moderate, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_02_07;
    target:src_ip;
)