Avast Free Antivirus & Comodo Firewall (settings, shields, performance)

Comodo Internet Security - CIS Firewall Help - CIS
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Originally posted in Avast Support Forums, however, I feel this may be interesting for Comodo users as well.

I’ve been using Avast Free AV combined with Comodo Firewall for a couple of years by now. I’ve researched the different forums for information on correct settings of both required to provide maximum possible protection and lowest interference and decrease in the overall system performance at the same time.

The basic settings scenario as far as the possible interaction between Avast and Comodo is concerned is as follows:

    1. In Avast all shields are enabled.
    1. In Comodo the Firewall is set in Custom mode.
    1. In Comodo the Defence+ is set in Safe mode.
    1. In Avast the Comodo folder is added to Exclusions in the File System Shield.
    1. In Avast all Comodo executables are added to Safe Processes in the Behaviour Shield .
    1. In Comodo the Avast is added to Exlusions in Shell-code detection.
    1. In Comodo avastsvc.exe, avastui.exe and avast.setup are added to Trusted applications under Network Security Policy/Application rules.
    1. The Sandbox is disabled in Avast and enabled in Comodo (I’ve tried it vice versa to no visible effect on performance).

Yesterday for some reason I turned off the Network Shield in Avast. And I’ve noticed an immediate and substantial increase in performance. The applications that were previously struggling to start for several seconds are now loaded in no time. Chrome loads twice as fast. Photoshop - too. Tested on two PCs - one an older Athlon with 1,5GB RAM (WinXP), the other - a Core i3-2350M with 8GB RAM (Win7 x64).

I’ve done some more reasearch on whether the Avast Network Shield is needed in the presence of a firewall. Unfortunately, I could get no clear answer to that. Most of the related discussions point to the fact that the Network Shield is one of the most economic Avast components performance-wise and should not produce any significant effect if combined with Comodo Firewall. I see just the opposite, however - the Network Shield in combination with Comodo will visibly slow down even a rather advanced hardware configuration. At the same time I am not sure if the turning off of the Network Shield is not a compromise to the overall security and how it may affect it.

So, any thoughts on this matter? How should one set up Avast Free and Comodo to provide maximum protection and not hamper performance?

P.S. I realize that the described situation might be a result of some settings in both applications that I’ve overlooked. But I’ve spent quite some time fiddling with those and until now the only detectable effect has been produced by turning off the Network Shield.

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Comodo does not believe in a network shield, and other additional shields (IM Shield, p2p shield, email shield, etc), and does not have one. With a network shield not there it cannot influence network performance.