alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET ADWARE_PUP Niagara Software Update Check"; flow:established,to_server; http.method; content:"POST"; http.uri; bsize:16; content:"/checkupdate.php"; http.host; content:"4t-niagara.com"; fast_pattern; threshold:type limit,count 1,seconds 300,track by_src; reference:md5,664a7f2d21f20f4a9747981145cb1332; classtype:trojan-activity; sid:2068528; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, tls_state TLSDecrypt, created_at 2026_04_01, deployment Perimeter, deployment SSLDecrypt, confidence High, signature_severity Informational, updated_at 2026_04_01, mitre_tactic_id TA0003, mitre_tactic_name Persistence, mitre_technique_id T1205, mitre_technique_name Traffic_Signaling; target:src_ip;)