ET MALWARE Possible Lockbit CnC Checkin

alert http [$HOME_NET,$HTTP_SERVERS] any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Possible Lockbit CnC Checkin";
    flow:established,to_server;
    http.method;
    content:"POST";
    http.uri;
    content:!".";
    content:"/?";
    content:"&";
    content:"="; within:8;
    http.accept_enc;
    content:"gzip,|20|deflate,|20|br"; fast_pattern;
    http.content_type;
    content:"text/plain";
    http.user_agent;
    pcre:"/(Mozilla\/5\.0\x20\x28Windows\x20NT\x206\.1|AppleWebKit\/587\.38\x20\x28KHTML,\x20like\x20Gecko|Chrome\/91\.0\.4472\.77|Safari\/537\.36|Edge\/91\.0\.864\.37|Firefox\/89\.0|Gecko\/20100101)/";
    http.header_names;
    content:"|0d 0a|Accept|0d 0a|Accept-Encoding|0d 0a|Content-Type|0d 0a|User-Agent|0d 0a|Host|0d 0a|Connection|0d 0a 0d 0a|"; startswith;
    http.request_body;
    content:"&=";
    content:"=";
    base64_decode:offset 0, relative;
    base64_data;
    pcre:"/^[\x20-\x7e\r\n]{0,13}[^\x20-\x7e\r\n]/";
    classtype:command-and-control;
    sid:2045316; rev:1;
    metadata:attack_target Client_Endpoint, created_at 2023_05_04, deployment Perimeter, malware_family LockBit, performance_impact Significant, confidence Medium, signature_severity Major, tag Ransomware, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_05_04, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;
)