TCP.Split.Handshake - Should I block it?

I would like to advise you to read the following article: http://watchguardsecurity...and-does-it-affect-me/

A piece of the story:

"First, you should know that this attack cannot punch holes in your firewall, willy-nilly, without user interaction. A key mitigating factor to the attack is that a client within your network must first make a connection to a malicious server on the internet, before this attack can even start. Some of the descriptions of the attack, which claim an external attacker can trick a firewall into giving them access as a trusted IP, seem to leave this fact out. So if you were worried that external attackers can just hop through your firewall on their own, don’t be."