alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE AMOS CnC Exfiltration - /joinsystem (POST)"; flow:established,to_server; urilen:11; http.method; content:"POST"; http.uri; content:"/joinsystem"; fast_pattern; http.header_names; content:!"|0d 0a|Referer|0d 0a|"; nocase; http.request_body; content:"BuildID="; startswith; content:"&user="; distance:0; reference:url,go.recordedfuture.com/hubfs/reports/cta-2024-0514.pdf; classtype:trojan-activity; sid:2052602; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2024_05_14, deployment Perimeter, malware_family AMOSStealer, confidence High, signature_severity Critical, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_05_14;)