My modem seems to be under “attack” every hour.
I’m seeing signs of port scanning and spoofing in the logs, like the one below.
Is there a more efficient way to block these attacks, like automatically blocking these IPs after some attempts?
Consider the router will be Flint 2
Just accept that they exist, it’s normal.
Try to disable ping answers if currently enabled. But all in all: Just ignore them. 
If you want to feel more secure, but this is kind of complicated, use fail2ban … For example see: Use of fail2ban
But if there is no service at the scanned ports, fail2ban is useless overhead. Only needed for https/ssh/or other exposed services.
Easier is not to expose services to the internet and ignore the useless scans (as said before).
