ET MALWARE Cobalt Strike Malleable C2 Profile (Teams) M1

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Cobalt Strike Malleable C2 Profile (Teams) M1";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/Collector/2.0/settings/"; startswith; fast_pattern;
    content:"events=";
    pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R";
    http.accept;
    content:"json"; bsize:4;
    http.referer;
    content:"https://teams.microsoft.com/_"; bsize:29;
    reference:url,www.blackarrow.net/leveraging-microsoft-teams-to-persist-and-cover-up-cobalt-strike-traffic/;
    classtype:command-and-control;
    sid:2032975; rev:1;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_05_18, deployment Perimeter, deployment SSLDecrypt, malware_family Cobalt_Strike, confidence Medium, signature_severity Major, updated_at 2021_05_18, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;
)