I now did uncheck "Log packets blocked by the default rule" and created 
a rule to block TCP/UDP on WAN with logging enabled.
This kind of works but it's not a very clean sollution. Will I still be 
able to open ports on my WAN as I created a rule before to block everything?

I did try to create a rule to block IGMP first (with no logging) as Fred 
mentioned, but the default rule would still log IGMP packets.
I could always allow IGMP, that way the packets wouldn't get logged, but 
can allowing IGMP be a security risk?

Thanks,
Timothy **