alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET USER_AGENTS Suspicious User-Agent (RT/1.0)"; flow:established,to_server; http.user_agent; content:"RT/1.0"; bsize:6; reference:md5,4c22c20fd816c11a3670100a40ac9dc0; classtype:trojan-activity; sid:2039422; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2022_10_17, deployment Perimeter, performance_impact Low, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_02_28, reviewed_at 2025_07_14;)