alert http1 $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike Beacon Activity (GET)"; flow:established,to_server; http.request_line; content:"|20|/logo|20|HTTP/1."; fast_pattern; http.method; content:"GET"; http.cookie; content:"lu="; startswith; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$/R"; http.header_names; content:!"Referer"; content:"|0d 0a|Accept|0d 0a|Host|0d 0a|Connection|0d 0a|Accept-Encoding|0d 0a|"; startswith; reference:md5,45ec8cee2c028e47d3bba2e14a93a957; classtype:trojan-activity; sid:2032336; rev:3; metadata:attack_target Client_Endpoint, created_at 2021_03_25, deployment Perimeter, confidence Medium, signature_severity Major, tag c2, updated_at 2024_04_04, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)