ET MALWARE APT33/CharmingKitten Shellcode Communicating with CnC

alert tcp $HOME_NET any -> $EXTERNAL_NET ![25,443,587,9997] (
    msg:"ET MALWARE APT33/CharmingKitten Shellcode Communicating with CnC";
    flow:established,to_server;
    dsize:<150;
    content:"|16 03|"; depth:2;
    content:"|00|"; distance:1; within:1;
    content:"|01 00 00|"; distance:1; within:3;
    content:"|03|"; distance:1; within:1;
    content:"|5b e0 37|"; distance:1; within:3; fast_pattern;
    content:"|00|"; distance:0;
    content:"|00|"; distance:1; within:1;
    content:"|00|"; distance:1; within:1;
    threshold:type limit, count 1, seconds 30, track by_dst;
    content:!"mtalk.google.com";
    reference:md5,a60f127a06e5b3dcacd1ec346f7995c5;
    classtype:targeted-activity;
    sid:2026576; rev:4;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_11_05, deployment Perimeter, malware_family Shellcode, performance_impact Low, confidence High, signature_severity Major, tag APT33_CharmingKitten, tag Shellcode, updated_at 2020_07_16;
)