ET MALWARE Buer Loader Update Request

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Buer Loader Update Request";
    flow:established,to_server;
    urilen:>200;
    http.method;
    content:"GET";
    http.uri;
    content:"/api/update/"; depth:12;
    pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R";
    http.user_agent;
    content:"Mozilla/5.0 (Windows NT 10.0|3b 20|Win64|3b 20|x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36";
    http.header_names;
    content:!"Accept";
    content:!"Referer";
    reference:md5,a8819db1fa758fd9f1d501dbb50f454f;
    classtype:command-and-control;
    sid:2029077; rev:2;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2019_11_12, deployment Perimeter, malware_family BuerLoader, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_10_21;
)