alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/Tofsee Connectivity Check M3"; flow:to_server,established; urilen:1; http.method; content:"GET"; http.user_agent; content:"Mozilla/5.0 |28|Windows NT 10.0|3b 20|Win64|3b 20|x64|29| AppleWebKit/537.36 |28|KHTML, like Gecko|29| Chrome/90.0.4430.85 Safari/537.36 OPR/76.0.4017.94"; bsize:131; http.host; content:"checkip.dyndns.org"; endswith; fast_pattern; http.header_names; content:!"Referer|0d 0a|"; reference:md5,cc171ee77dc2d657e0c018fcad17608f; classtype:trojan-activity; sid:2033325; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2021_07_15, deployment Perimeter, malware_family Win32_Tofsee, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2021_07_15;)