ET MALWARE Likely APT29 Retrieving Payload Embedded In PNG

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"ET MALWARE Likely APT29 Retrieving Payload Embedded In PNG";
    flow:established,to_server;
    http.method;
    content:"GET";
    http.uri;
    content:".png";
    http.user_agent;
    content:"Mozilla/5.0 (Windows NT 6.1|3b 20|WOW64) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6"; fast_pattern; bsize:105;
    http.header_names;
    content:!"Accept";
    content:!"Referer|0d 0a|";
    reference:url,researchcenter.paloaltonetworks.com/2016/09/unit42-the-dukes-rd-finds-a-new-anti-analysis-technique/;
    classtype:targeted-activity;
    sid:2044212; rev:5;
    metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2016_08_31, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Major, updated_at 2023_02_16, former_sid 2821945;
)