Traffic blocked from other machines on network

I received a pop-up message yesterday that SEP is blocking traffic from my kernel. I looked at my logs, and the Network Threat Protection log shows SEP is blocking traffic from a number of machines on our network.

Remote ports range from 1053 to 64053. All traffic is being directed to either my port 139 or port 445. All packets are being blocked by the Block Local File Sharing rule. None of the remote users has occasion to be making SMB or NetBIOS connections to my machine. FWIW, all but one of the 10 remote machines from which traffic is being blocked is a Mac.

Is this a situation that warrants further investigation? I'm attaching my NTP log.