alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Grizzly Loader Custom HTTP Header Observed (X-Panel-Callback)"; flow:established,to_server; http.header; pcre:"/X-Panel-Callback\x3a\x20\d{1,2}[\r\n]/"; http.header_names; content:"|0d 0a|x-panel-callback|0d 0a|"; nocase; fast_pattern; threshold:type limit,count 1,seconds 300,track by_src; classtype:trojan-activity; sid:2071883; rev:1; metadata:affected_product Windows_Client, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_09_01, deployment Perimeter, deployment SSLDecrypt, malware_family GrizzlyLoader, confidence Medium, signature_severity Major, tag c2, updated_at 2026_09_01, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1071, mitre_technique_name Application_Layer_Protocol; target:src_ip;)