SMB: Invalid Protocol
This protocol anomaly is an invalid SMB protocol. The first four bytes of valid SMB messages are 0xff, "S," "M," "B." This can be a misbehaving client or an attempt to tunnel through the NETBIOS port.
References
srx-branch-12.3
srx-19.3
srx-branch-19.3
vsrx3bsd-19.2
srx-branch-19.4
vsrx-19.4
mx-12.3
mx-19.4
vmx-19.4
mx-19.3
vsrx3bsd-19.4
srx-19.4
vsrx-12.3
vmx-19.3
vsrx-19.2
srx-12.3