alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE LeChiffre Ransomware CnC"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/sipvoice.php?"; startswith; fast_pattern; content:"&session="; distance:0; http.header; header_lowercase; content:"keep-alive|3a 20|300"; http.user_agent; content:"Mozilla/4.0 (compatible|3b 20|Synapse)"; startswith; http.header_names; to_lowercase; content:!"|0d 0a|accept"; content:!"|0d 0a|referer|0d 0a|"; reference:md5,4523ccfd191dcceeae8e884f82f5c7ad; reference:url,blog.malwarebytes.org/intelligence/2016/01/draft-lechiffre-a-manually-run-ransomware/; classtype:command-and-control; sid:2022406; rev:6; metadata:attack_target Client_Endpoint, created_at 2016_01_25, deployment Perimeter, signature_severity Major, tag Ransomware, updated_at 2024_05_02, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)