DOS Block

My Draytek router is frequently sending me an email of which this is typical:

2014/06/09 09:52:00 -- [DOS][Block][syn_flood, timeout=10][192.168.202.203:53553->208.78.94.72:80][TCP][HLen=20, TLen=64, Flag=S, Seq=2621011111, Ack=0, Win=65535]

And here's another variation:
2014/06/09 09:04:43 -- [DOS][Block][tcp_flag, scanner=fin_wo_ack][192.168.202.211:49390->173.194.34.90:80][TCP][HLen=20, TLen=52, Flag=F, Seq=2803993150, Ack=0, Win=65535]

What proactive action should I take or is it something I need not worry about?

are you running the 192.xxx.xxx.xx IP address on your pc. If so your pc looks to be running an attack on an outside internet IP address that your router is detecting.

I may have this wrong but I would run a virus scan asap........

The LAN IPs are allocated to a couple of mobile phones and unsurprisingly there is no AV programs loaded onto them. What you appear to be suggesting is that they have been compromised in some way.

So it looks as though ESET Mobile Security - Home Edition should be installed. Would that resolve the problem?

However
208.78.94.72 is some company in the US
173.194.34.90 is Google
Could it be some app on the phone that is actually required but prevented from communicating with base because of firewall rules in the router?

False positive or trash internet traffic. Router DoS protection is useless. Nothing to worry about.

as the other person said, looks like this may be a false positive, especially as you have mobile phones attached. It is up to you about using a mobile av solution. What you need is a outbound firewall check that validates the mobile app sending out and asks you for a yes/no allow. That way you can tell what is generating the traffic from the mobile.

It's fine, ignore it. Not worth investigating further or taking any action over.