I got this in my router log, what does it means and solution to it.
Thanks.

Use firewall to protect your router http://wiki.mikrotik.com/wiki/Firewall
Still asking, any threat to my Network(router)? Just curious to know.Though I will do as suggested.
Thanks.
yes it is a threat. consider yourself lucky this time. Get your firewall up. Gregg sowell has a very good tutorial on this subject.
My home mikrotik got hacked by the Chinese! They re-routed google to youdao. Pretty funny actually, but has taught me to secure even the smallest of installations with a decent firewall / password.