alert tcp $HOME_NET any -> $EXTERNAL_NET [1024:] (msg:"ET MALWARE NanoCore RAT Keepalive 3"; flow:established,to_server; dsize:68; content:"|40 00 00 00|"; depth:4; content:!"|00 00 00 00|"; within:4; threshold:type both, track by_src, count 10, seconds 120; flowbits:set,ET.NanoCore; flowbits:noalert; reference:md5,bf994dce3712fb66afa4a2ce5b3ceee4; reference:url,medium.com/@the_abjuri5t/nanocore-rat-hunting-guide-cb185473c1e0; classtype:trojan-activity; sid:2046912; rev:3; metadata:attack_target Client_Endpoint, created_at 2015_04_04, deployment Perimeter, malware_family NanoCore, performance_impact Moderate, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2023_07_26, former_sid 2810452;)