ET MALWARE Possible OSX/SHLAYER Checkin M2

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Possible OSX/SHLAYER Checkin M2";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:"/rga?a="; startswith; fast_pattern;
    content:"&b="; within:10;
    pcre:"/^[A-F0-9]{8}\-[A-F0-9]{4}\-[A-F0-9]{4}\-[A-F0-9]{4}\-[A-F0-9]{12}$/R";
    http.user_agent;
    content:"Go-http-client/1.1";
    http.header_names;
    content:"|0d 0a|Host|0d 0a|User-Agent|0d 0a|Accept-Encoding|0d 0a 0d 0a|"; bsize:39;
    threshold:type limit, count 1, seconds 600, track by_dst;
    classtype:trojan-activity;
    sid:2038613; rev:1;
    metadata:affected_product Mac_OSX, attack_target Client_Endpoint, created_at 2022_08_25, deployment Perimeter, malware_family Shlayer, performance_impact Low, confidence Low, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_08_25;
)