alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Downeks Variant CnC Beacon"; flow:established,to_server; http.method; content:"POST"; http.uri; content:!"."; content:!"?"; content:!"="; http.header; content:"Content-Type|3a 20|text/plain|3b|charset=UTF-8|0d 0a|Host|3a 20|"; depth:46; fast_pattern; content:"Expect|3a 20|100-continue|0d 0a|"; distance:0; http.request_body; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})+$/"; http.header_names; content:!"User-Agent|0d 0a|"; content:!"Accept"; content:!"Referer|0d 0a|"; reference:md5,31cf042e91de7492c86e1ad02dc9eaec; reference:url,researchcenter.paloaltonetworks.com/2017/01/unit42-downeks-and-quasar-rat-used-in-recent-targeted-attacks-against-governments/; classtype:command-and-control; sid:2023811; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_01_31, deployment Perimeter, malware_family DustSky_related_Implant, confidence High, signature_severity Major, tag c2, updated_at 2020_08_04, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)