How does a firewall affect speed?

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A firewall protects your computer from hackers and malicious software by monitoring its connection ports and blocking unauthorised intrusions. However, while a firewall must necessarily use some of your computer’s resources, it shouldn’t grind your system to a standstill.

If your computer seems to be running slowly, choose a firewall program designed to have a minimum impact on your system’s resources.

System performance

Firewall software works silently in the background, monitoring incoming and outgoing Internet and network traffic. Like all programs, it integrates with your computer’s central processor and uses system memory. The computing power and memory needed for the program to function effectively impacts on your computer’s speed and performance, but this may be barely noticeable in well-designed software that integrates seamlessly with the Windows operating system. However, badly designed firewalls can slow down your computer by as much as 25 percent, PC World reports.

Internet performance

A firewall can potentially slow down your Internet speed because it monitors communications from the Internet. However, this slowdown should not be significant unless you have selected a high security option that gives your firewall more work to do. The default option is suitable for most home users and shouldn’t impact significantly on your Internet performance.

Software conflicts

Running two firewall programs simultaneously can cause software conflicts and significantly slow down your computer. Windows computers running XP, Vista and Windows 7 and 8 have a built-in firewall that is switched on by default. Ensure that the Windows firewall is disabled if you've opted to use a third-party firewall. To turn off the firewall in Windows 8, log into your user account to bring up the "Metro" interface. Point your mouse to the lower right-hand corner of the screen; this brings up a sidebar menu on the right side of the screen. Click on the sidebar’s “Control Panel” option to open the Control Panel. Click on “System and security,” then click on “Turn Windows Firewall on or off." Select the option to turn the firewall off.


Firewalls typically run alongside, and are sometimes incorporated into, other software programs designed to block viruses and adware. This combination of background software can slow down your system, even if your firewall alone isn’t hard on resources. Turning off unnecessary programs running in the background can help speed up your computer because this frees more space for your firewall and antivirus software running in the background. If this doesn’t help, try turning off your firewall or antivirus software when your computer isn’t connected to the Internet. Defragmenting your hard drive regularly, removing desktop clutter and deleting temporary Internet files also frees up memory and disc space, enabling your computer to handle tasks more quickly and efficiently. Installing more memory can also significantly boost performance.

Software and hardware firewalls

Software firewalls, the more popular choice for home users, have the potential to slow down your computer because they use its resources. Hardware firewalls, mainly used by businesses, don’t do this because, being normally connected to a broadband router, they don’t need to be integrated with computer resources to work effectively. Both hardware and software firewalls can potentially slow down Internet speed if their security settings are high.