Rule History

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE [ANY.RUN] Win32/ObserverStealer CnC Activity (Loading) M1"; flow:established, to_server; http.method; content:"GET"; http.uri; content:"/?id="; startswith; fast_pattern; pcre:"/^\/\x3fid\x3d([0-9a-f]{8})-([0-9a-f]{4})-([0-9a-f]{4})-([0-9a-f]{4})-([0-9a-f]{12})$/"; http.host; pcre:"/^(?:(?:\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])(:\d{2,5})?$/R"; http.accept; content:"|2a 2f 2a|"; bsize:3; http.accept_enc; content:"gzip|2c 20|deflate"; bsize:13; http.connection; content:"Keep-Alive"; bsize:10; http.user_agent; content:"Mozilla|2f|4|2e|0|20 28|compatible|3b 20|MSIE|20|7|2e|0|3b 20|Windows|20|NT|20|6|2e|3|3b 20|WOW64|3b 20|Trident|2f|7|2e|0|3b 20 2e|NET4|2e|0C|3b 20 2e|NET4|2e|0E|3b 20 2e|NET|20|CLR|20|2|2e|0|2e|50727|3b 20 2e|NET|20|CLR|20|3|2e|0|2e|30729|3b 20 2e|NET|20|CLR|20|3|2e|5|2e|30729|29|"; http.header_names; content:"Accept|0d 0a|Accept-Encoding|0d 0a|User-Agent|0d 0a|Host|0d 0a|Connection|0d 0a 0d 0a|"; bsize:59; reference:md5,c28cc92a7c78b96bec58fa3e5398074a; reference:url,community.emergingthreats.net/t/observerstealer/624; reference:url,app.any.run/tasks/5728c30e-00c1-4f87-9522-ff8b9e08fa32/; classtype:trojan-activity; sid:2046169; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2023_06_07, deployment Perimeter, malware_family ObserverStealer, performance_impact Moderate, confidence High, signature_severity Critical, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_06_08;)