alert tcp $EXTERNAL_NET [1024:] -> $HOME_NET any (msg:"ET MALWARE NanoCore RAT Keepalive Response 4"; flow:established,to_client; dsize:29; content:"|19 00 00 00 01|"; depth:5; fast_pattern; flowbits:isset,ET.NanoCore; threshold:type both, track by_src, count 10, seconds 120; reference:md5,bf994dce3712fb66afa4a2ce5b3ceee4; reference:url,medium.com/@the_abjuri5t/nanocore-rat-hunting-guide-cb185473c1e0; classtype:trojan-activity; sid:2046920; rev:2; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2017_10_24, deployment Perimeter, malware_family NanoCore, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_07_26, reviewed_at 2023_12_13, former_sid 2828398;)