alert tcp $EXTERNAL_NET [!2504,!2505,!2032,1024:] -> $HOME_NET any (msg:"ET MALWARE NanoCore RAT Keepalive Response 1"; flow:established,to_client; dsize:36; content:"|20 00 00 00|"; depth:4; content:!"|F0 DE BC 0A|"; within:5; content:!"|00 00 00 00|"; within:4; content:!"|20 00 00 00 01 00 00 00|"; depth:8; content:!"|20 00 00 00 eb 6e 00 00 00 00 00 00 08|"; depth:13; flowbits:isset,ET.NanoCore; threshold:type both, track by_src, count 10, seconds 120; stream_size:client, <, 5000; reference:md5,bf994dce3712fb66afa4a2ce5b3ceee4; reference:url,medium.com/@the_abjuri5t/nanocore-rat-hunting-guide-cb185473c1e0; classtype:trojan-activity; sid:2046909; rev:10; metadata:attack_target Client_Endpoint, created_at 2015_03_27, deployment Perimeter, malware_family NanoCore, performance_impact Moderate, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_07_26, former_sid 2810290;)