alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Bisonal CnC Checkin"; flow:established,to_server; http.uri; content:".txt"; pcre:"/^\/[a-z]{4}(?:\d{1,3}\.){3}\d{1,3}[a-z]{6}\.txt/"; http.user_agent; bsize:68; content:"Mozilla|2f|4|2e|0|20 28|compatible|3b 20|MSIE|20|6|2e|0|3b 20|Windows|20|NT|20|5|2e|0|3b 20 2e|NET|20|CLR|20|1|2e|1|2e|4322"; fast_pattern; http.header_names; content:"|0d 0a|User-Agent|0d 0a|Host|0d 0a|"; startswith; reference:md5,CC71620DE7216B186DA2C9BA06703613; reference:url,researchcenter.paloaltonetworks.com/2018/07/unit42-bisonal-malware-used-attacks-russia-south-korea/; reference:url,blog.talosintelligence.com/2020/03/bisonal-10-years-of-play.html; classtype:command-and-control; sid:2025922; rev:6; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2018_07_31, deployment Perimeter, malware_family Bisonal, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2024_03_12;)