alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Linux/Moose NAT Traversal CnC Beacon set"; flow:established,to_server; dsize:4; content:"|18 00 00 00|"; fast_pattern; flowbits:set,ET.Linux.Moose; flowbits:noalert; reference:url,welivesecurity.com/wp-content/uploads/2015/05/Dissecting-LinuxMoose.pdf; classtype:command-and-control; sid:2021150; rev:2; metadata:attack_target Client_Endpoint, created_at 2015_05_26, deployment Perimeter, signature_severity Major, tag c2, updated_at 2019_10_08, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)