alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Cobalt Strike Activity (GET)"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/image-directory/br.ico"; fast_pattern; http.header; content:"Connection|3a 20|Close|0d 0a|"; http.user_agent; content:"Mozilla/5.0|20|(iPhone|3b 20|CPU|20|iPhone|20|OS|20|12_0|20|like Mac|20|OS|20|X)|20|AppleWebKit/605.1.15|20|(KHTML,|20|like|20|Gecko)|20|Version/12.0"; bsize:108; http.header_names; content:!"Referer"; http.accept; content:"image/*"; bsize:7; reference:md5,efcf2797aaa1ff0bb8914aba8e3a5e15; reference:url,thedfirreport.com/2021/08/16/trickbot-leads-up-to-fake-1password-installation/; classtype:trojan-activity; sid:2033820; rev:2; metadata:attack_target Client_Endpoint, created_at 2021_08_27, deployment Perimeter, malware_family Cobalt_Strike, confidence Medium, signature_severity Major, updated_at 2021_08_27, mitre_tactic_id TA0011, mitre_tactic_name Command_And_Control, mitre_technique_id T1001, mitre_technique_name Data_Obfuscation;)