alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"🐾 - 🚨 Suspicious TLS Certificate - Possible 👿 BianLian Ransomware 🔒 flow with C2 Server"; flow:established,to_client; tls.cert_issuer; content:"C="; startswith; pcre:"/C=[a-zA-Z0-9]{16}/"; pcre:"/O=[a-zA-Z0-9]{16}/"; pcre:"/OU=[a-zA-Z0-9]{16}/"; tls.cert_subject; content:"C="; startswith; pcre:"/C=[a-zA-Z0-9]{16}/"; pcre:"/O=[a-zA-Z0-9]{16}/"; pcre:"/OU=[a-zA-Z0-9]{16}/"; reference:url,https://malpedia.caad.fkie.fraunhofer.de/details/win.bianlian; reference:url,https://redacted.com/blog/bianlian-ransomware-gang-gives-it-a-go/; reference:url,https://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/Trojan.Win64.BIANLIAN.B.go/; reference:url,https://blogs.blackberry.com/en/2022/10/bianlian-ransomware-encrypts-files-in-the-blink-of-an-eye; reference:url,https://decoded.avast.io/threatresearch/decrypted-bianlian-ransomware/; reference:url,https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-136a; metadata:attack_target Client_and_Server, signature_severity Major, affected_product Windows_XP_Vista_7_8_10_11_Server_32_64_Bit, mitre_tactic_id TA0011, mitre_tactic_name Command_and_Control, mitre_technique_id T1071.001, mitre_technique_name Application_Layer_Protocol_Web_Protocols, created_at 2023_06_30, updated_at 2024_02_21; sid:3300691; rev:7; classtype:command-and-control;)