alert udp $EXTERNAL_NET 1024: -> $HOME_NET any (msg:"ET MALWARE Suspected BPFDoor UDP Magic Packet (Inbound)"; content:"|72 55|"; startswith; fast_pattern; reference:url,exatrack.com/public/Tricephalic_Hellkeeper.pdf; reference:url,elastic.github.io/security-research/intelligence/2022/05/04.bpfdoor/article/; classtype:trojan-activity; sid:2036751; rev:1; metadata:attack_target Client_Endpoint, created_at 2022_06_01, deployment Perimeter, malware_family BPFDoor, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_06_01;)