ET MALWARE FormBook CnC Checkin (GET)

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE FormBook CnC Checkin (GET)";
    flow:established,to_server;
    content:"Connection|3a 20|close|0d 0a 0d 0a 00 00 00 00 00 00|"; fast_pattern;
    http.method;
    content:"GET";
    http.uri;
    content:"/?";
    pcre:"/^[A-Za-z0-9_\-]{1,15}=(?:[A-Za-z0-9_\-]{1,25}|(?:[A-Za-z0-9\+\/]{4})*(?:[A-Za-z0-9\+\/]{2}==|[A-Za-z0-9\+\/]{3}=|[A-Za-z0-9\+\/]{4}))&[A-Za-z0-9_\-]{1,15}=(?:[A-Za-z0-9_\-]{1,25}|(?:[A-Za-z0-9\+\/]{4})*(?:[A-Za-z0-9\+\/]{2}==|[A-Za-z0-9\+\/]{3}=|[A-Za-z0-9\+\/]{4}))(?:&sql=\d*)?$/R";
    http.connection;
    content:"close"; depth:5; endswith;
    http.header_names;
    content:"|0d 0a|Host|0d 0a|Connection|0d 0a 0d 0a|"; depth:22; endswith;
    reference:md5,a6a114f6bc3e86e142256c5a53675d1a;
    classtype:command-and-control;
    sid:2031412; rev:10;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_12_19, deployment Perimeter, malware_family Formbook, performance_impact Moderate, confidence Medium, signature_severity Major, updated_at 2023_08_10, reviewed_at 2024_02_13;
)