alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Possible APT 41 Fake Server Response"; flow:established,from_server; http.stat_code; content:"200"; http.server; content:"Microsoft-IIS|2f 20|10.0|20|Microsoft-HTTPAPI/2.0"; fast_pattern; reference:url,www.welivesecurity.com/wp-content/uploads/2019/10/ESET_Winnti.pdf; classtype:command-and-control; sid:2028837; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, created_at 2019_10_16, deployment Perimeter, malware_family LOWKEY, performance_impact Low, confidence Medium, signature_severity Major, tag APT41, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_04_16;)