Judging from the logs you are running a Docsis type router right? If thats the case then the blocked SYNC floods are just communications from your ISP to your router which most Docsis based routers have a problem with.
If you want to have better logs you can use a third party program to fetch your logs and show them in a more graphical way like
PRTG (paessler.com) but how much this is going to help you i dunnot know since Docsis type routers have limited options.
Anyway next time you post a log, please add a text file rather then copy pasting the log like this.
Cheers