alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE LeChiffre Ransomware CnC"; flow:to_server,established; http.method; content:"GET"; http.uri; content:"/sipvoice.php?"; depth:14; fast_pattern; content:"&session="; distance:0; http.header; content:"Keep-Alive|3a 20|300"; http.user_agent; content:"Mozilla/4.0 (compatible|3b 20|Synapse)"; startswith; http.header_names; content:!"Accept"; content:!"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:3; metadata:attack_target Client_Endpoint, created_at 2016_01_25, deployment Perimeter, signature_severity Major, tag Ransomware, updated_at 2020_06_17, mitre_tactic_id TA0040, mitre_tactic_name Impact, mitre_technique_id T1486, mitre_technique_name Data_Encrypted_for_Impact;)