alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Specter Insight Beacon CnC Checkin M1"; flow:established,to_server; http.method; content:"GET"; http.uri; bsize:62<>66; content:"/threads/"; startswith; pcre:"/^[a-f0-9]{32}/R"; content:"/messages|3f|filter|3d|"; within:17; pcre:"/^\d{5,7}$/R"; http.user_agent; bsize:16; content:"Evernote Windows"; fast_pattern; reference:url,practicalsecurityanalytics.com/specterinsight/; reference:md5,612e27b5df944f1591bfc5d1bc17a153; classtype:trojan-activity; sid:2061025; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, affected_product Windows_11, attack_target Client_and_Server, tls_state plaintext, created_at 2025_03_24, deployment Perimeter, malware_family Specter_Insight, performance_impact Low, confidence High, signature_severity Major, tag C2_Framework, updated_at 2025_04_14, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1567, mitre_technique_name Exfiltration_Over_Web_Service;)