Impact to the internet speed when creating firewall exceptions

Question

Hey there, 
 
 How much of an impact to the internet speed does it make, if I create a new firewall exception? 
 
 Since the firewall has to go through the entire ruleset, it should slow down every request a little bit. 
 
 Is there an upper bound of exceptions I should create, or a formular of how much every exception slows the traffic down? 
 
 Thanks for your thoughts. 
 
 David

Michael Dunn · Accepted Answer

Yes that is a well written regex. There are customers running with several hundred of them written like this that have no problem. There is no specific limit. It is like... how many pencils can you carry? Each individual pencil is lightweight and you can carry many at a time. Generally you would not worry about it. But if you are also carrying bricks then suddenly every gram counts and you want to look at the pencils. And if you put "google.com" into the regex it suddenly is a pencil that weighs 5x as much. If you put "*.google.com.*maps" it weighs 20x as much. Note that the only impact of regex is CPU processing. I have seen customer boxes with CPU issues (mostly due to other stuff) and poorly written regex. Improving the quality of the regex made a noticeable difference in CPU usage.

Michael Dunn · Answer

It may depend on what specific "exception" type you are talking about. Within the Web Filter, the Web Exceptions have high performance as long as correct RegEx is written. Poor Regex or putting in FQDNs into the RegEx field results in poor performance. Within firewall rules, I firewall rule that relies on FQDN Host objects in the Source or Destination has an impact to performance because it need to do an additional FQDN to IP lookup for every new connection. If you only have a few this is not a problem, however I have seen customers create dozens of FQDN hosts and putting them in firewall rules as a way of creating an "exception" to allow traffic. Related is this article: https://support.sophos.com/support/s/article/KBA-000008111?language=en_US

Vivek Jagad · Answer

Hi David Grahammer , 
 Thank you for reaching out to the community, creating a firewall exception can have both a positive and negative impact on internet speed. 
 Positive impact: 
 - By creating a firewall exception for specific applications or services, you can allow them to bypass the firewall and communicate freely over the network. This can lead to faster speeds for those specific applications as they are no longer being restricted by the firewall. 
 Negative impact: 
 - However, creating firewall exceptions can also pose security risks as it allows potentially malicious software to communicate freely over the network. This can slow down internet speed as the firewall has to work harder to monitor and block any potentially harmful traffic. 
 Overall, the impact on internet speed from creating a firewall exception will depend on the specific circumstances and how carefully the exception is configured to balance speed and security.

Impact to the internet speed when creating firewall exceptions

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