Hello. I have been working with routeros and some mikrotik boards for a few months now and loving what this little guy can do (RB450G). I have hit a roadblock in trying to figure out how to setup a firewall rule to stop ping on my WAN IP. My router is on the edge of my network and has a public static IP in it from my ISP. My question is, how do I turn off ping responses from the WAN so that when anyone from over the internet tries to ping me it fails? I don’t care about the internal network that I have setup here as all of those devices are mine. I have this unit performing nat for me as well. I have searched the forums and wikis but I see all kinds of other scenarios of stopping ping to the WAN (i.e. Stopping ping from LAN side of your Mikrotik) but nothing in regards to blocking people from pinging from the WAN side. Thanks very much in advance! 
You would need to create some firewall rules with the chain of input.
Here is example
/ip firewall filter add chain=input protocol=icmp action=drop in-interface=WAN
This would drop all ICMP traffic coming in your WAN interface.
I would highly recommend putting in your input rules for what you want to have access to your router and then create a input drop rule at the end. Make sure you allow yourself access though. If you need example of this style of rules let me know. But MT has an accept all by default.
Ben
post your /firewall filter export.
Like AKJP mentioned you should create some allowance rules for the connections you want and end with an explicit drop rule.
There should be a default filter rule for this under IP → Firewall, if you look in the list of filter rules it will list ICMP in the protocol column. You can simply change this rule from accept to drop and the WAN responding to a ping issue will be resolved.