alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Ursnif Variant CnC Beacon 4"; flow:established,to_server; urilen:>125; http.method; content:"GET"; http.uri; content:"."; pcre:"/\.(?:gif|bmp|jpeg|png)$/"; http.user_agent; bsize:50; content:"Mozilla/4.0 (compatible|3b 20|MSIE 8.0|3b 20|Windows NT 6.1)"; fast_pattern; http.connection; bsize:10; content:"Keep-Alive"; http.header_names; content:!"|0d 0a|Accept"; content:!"|0d 0a|Referer|0d 0a|"; content:"|0d 0a|User-Agent|0d 0a|Host|0d 0a|"; content:"|0d 0a|Connection|0d 0a|"; distance:0; pcre:"/\x0d\x0aUser-Agent\x0d\x0aHost\x0d\x0a(?:Content-Length\x0d\x0a)?Connection\x0d\x0a(?:Cache-Control|Pragma)\x0d\x0a\x0d\x0a$/"; reference:md5,f870c0d62691fc39194922e4a59fdc1c; classtype:command-and-control; sid:2021829; rev:6; metadata:attack_target Client_Endpoint, created_at 2015_09_24, deployment Perimeter, signature_severity Major, tag c2, updated_at 2024_03_12, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)