alert http1 $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE [ANY.RUN] Win32/ObserverStealer CnC Activity (Loading) M2"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/s?id="; startswith; fast_pattern; pcre:"/^\/s\x3fid\x3d([0-9a-f]{8})-([0-9a-f]{4})-([0-9a-f]{4})-([0-9a-f]{4})-([0-9a-f]{12})$/"; 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; bsize:3; content:"|2a 2f 2a|"; http.accept_enc; bsize:13; content:"gzip|2c 20|deflate"; http.connection; bsize:10; content:"Keep-Alive"; http.user_agent; content:".NET"; http.header_names; bsize:59; content:"Accept|0d 0a|Accept-Encoding|0d 0a|User-Agent|0d 0a|Host|0d 0a|Connection|0d 0a 0d 0a|"; 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:2046170; rev:5; 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, confidence High, signature_severity Critical, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_04_07, reviewed_at 2024_01_26;)