ET MALWARE Cobalt Strike Activity (GET)

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Cobalt Strike Activity (GET)";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/image-directory/br.ico"; fast_pattern;
    http.header;
    content:"Connection|3a 20|Close|0d 0a|";
    http.user_agent;
    content:"Mozilla/5.0|20|(iPhone|3b 20|CPU|20|iPhone|20|OS|20|12_0|20|like Mac|20|OS|20|X)|20|AppleWebKit/605.1.15|20|(KHTML,|20|like|20|Gecko)|20|Version/12.0"; bsize:108;
    http.header_names;
    content:!"Referer";
    http.accept;
    content:"image/*"; bsize:7;
    reference:md5,efcf2797aaa1ff0bb8914aba8e3a5e15;
    reference:url,thedfirreport.com/2021/08/16/trickbot-leads-up-to-fake-1password-installation/;
    classtype:trojan-activity;
    sid:2033820; rev:2;
    metadata:attack_target Client_Endpoint, created_at 2021_08_27, deployment Perimeter, malware_family Cobalt_Strike, confidence Medium, signature_severity Major, updated_at 2021_08_27, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;
)