alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Kimsuky Related CnC Activity"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/ugd/"; fast_pattern; pcre:"/^[a-z0-9]{6}_[a-z0-9]{32}/R"; content:".txt"; endswith; http.user_agent; content:"Mozilla/4.0|20|(compatible|3b 20|Win32|3b 20|WinHttp.WinHttpRequest.5)"; http.header; content:"Connection|3a 20|Keep-Alive"; nocase; http.header_names; content:!"Referer"; reference:md5,d74f268b986fecfa03b81029dd134811; reference:url,github.com/eset/malware-ioc/tree/master/kimsuky/hotdoge_donutcat_case; classtype:trojan-activity; sid:2034698; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_12_13, deployment Perimeter, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_12_13;)