alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE FoggyWeb Backdoor Incoming Request (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/adfs/portal/images/theme/light01/"; startswith; content:".webp"; endswith; reference:url,www.microsoft.com/security/blog/2021/09/27/foggyweb-targeted-nobelium-malware-leads-to-persistent-backdoor; classtype:command-and-control; sid:2034034; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Server, created_at 2021_09_28, deployment Perimeter, deployment Internal, deployment SSLDecrypt, malware_family FoggyWeb, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_09_28;)