alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE CloudAtlas APT Related Maldoc Activity M4 (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/?"; startswith; content:"_"; within:10; content:".html"; within:15; isdataat:20,relative; http.user_agent; content:"|3b 20|ms-office|3b 20|"; http.header_names; content:!"Referer"; reference:md5,0957edfec31dd2dd05d484eed90593c7; reference:url,www.facct.ru/blog/cloud-atlas; classtype:trojan-activity; sid:2049734; rev:1; metadata:attack_target Client_Endpoint, created_at 2023_12_19, deployment Perimeter, deployment SSLDecrypt, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_12_19; target:src_ip;)