alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE APT33/CharmingKitten Encrypted Payload Inbound"; flow:established,from_server; flowbits:isset,ET.APT33CharmingKitten.1; http.stat_code; content:"200"; http.header; content:"|0d 0a|CacheControl|3a 20|"; fast_pattern; file.data; pcre:"/^(?:[A-Z0-9+\/]{4})*(?:[A-Z0-9+\/]{2}==|[A-Z0-9+\/]{3}=|[A-Z0-9+\/]{4})$/i"; reference:md5,9881bccf12fd8ae71a03247d2ad61a06; classtype:targeted-activity; sid:2026578; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_11_05, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag APT33, tag CharmingKitten, updated_at 2020_08_27;)