alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Chrysalis Backdoor CnC Checkin"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/a/chat/s/"; fast_pattern; http.user_agent; content:"Mozilla|2f|5|2e|0|20 28|Windows|20|NT|20|10|2e|0|3b 20|Win64|3b 20|x64|29 20|AppleWebKit|2f|537|2e|36|20 28|KHTML|2c 20|like|20|Gecko|29 20|Chrome|2f|80|2e|0|2e|4044|2e|92|20|Safari|2f|537|2e|36"; http.host; content:!"deepseek.com"; reference:url,rapid7.com/blog/post/tr-chrysalis-backdoor-dive-into-lotus-blossoms-toolkit/; classtype:command-and-control; sid:2067265; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, affected_product Windows_11, affected_product Windows_8, affected_product Windows_10, affected_product Notepad__, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_02_02, deployment Perimeter, deployment SSLDecrypt, malware_family Chrysalis, performance_impact Low, confidence Medium, signature_severity Major, tag Backdoor, tag c2, updated_at 2026_02_03, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol;)