Comodo Firewall conflict with Avast Pro Antivirus [v6]

I recently installed Comodo Firewall with Defense+ on my computer which already had Avast Pro Antivirus. It wreaked havoc. Some programs didn’t open. I got an error message saying that system can’t find the file. System even got stuck sometimes. Had to press and hold the power button to turn it off as the shutdown function didn’t work. Is this a known issue?

I would put the first – Comodo FW. Avast antivirus (only). Comodo have defender. So there is a conflict.
Leave on only Avast AV and Comodo FW.
Turn off Avast FW.

Add this one to the other in a trusted.

I didn’t install Avast IS. Just the Antivirus. So there’s no firewall to disable.

You added them to each other in a trusted?
You turn off Avast before installing Comodo FW?
The firewall is turned off Windows?
What OS?

P.S. I would put the first – Comodo FW.
But if you have to reinstall, you it will need to remove all the traces of Avast IS!

Thank you very much for your issue report.

We would very much appreciate it if you would be kind enough to edit your report to put it in the standard format and add any additional information requested, as this will make it much easier for the developers to diagnose and fix the problem.

The reasons we need all the information in the format, though they may not seem directly relevant to the issue are explained here.

If you are able to do this we will forward this post to the format verified board, where it is more likely to get looked at by developers. You can find assistance using red links in the format and here. If you need further help please ask a mod. If you do not add the information after a day or two we will forward this post to the non-format board. If this happens we will tell you how to rectify this if you wish to.

In the current process we will normally leave it up to you whether you want to make a report in standard format or not. However we may remind you if we think a bug of particular importance.

Many thanks again


Also you may find the FAQ here:;msg669385#msg669385 helpful

I would probably have a go at the ‘recommended options’ at least before posting the bug report. If they work, a report is optional, otherwise, please do post one.

Turning WebShield off has helped some users, but probably you have not installed it.

Do you have Comodo Firewall version 5 or 6? Also which Avast version do you have?

If you have Comodo Firewall 6 you not the only one who face such issues with Avast 8 if you use this version they don’t get along. Many report black-screens, BSOD, system freeze, slow boot-up, etc.

I also heard from some ppl that even Comodo Firewall version 5 don’t get along with Avast 8 now.

The Q here who is going to fix this? Comodo or Avast?

Comodo Firewall 6 with Defense+ and Avast Pro Antivirus 8.

Well both the companies released their v6 and v8 in a hurry. In the latest build of Comodo IS they say 200+ bugs have been fixed. I’m a member at Avast forums too and I can see many users reporting various kinds of issues. So I guess both programs are not yet ready for public use. Beginner users may find them completely unusable with these issues. Sad to see this happening to two of my favourite security software.

From the information you have given I am not clear whether this is a bug/issue.

For the moment I will transfer you to help so you can work through this issue with users and mods in this forum and hopefully resolve it. I hope that is OK.

Please ask any mod to move this report back to the bugs forum if it becomes clear that it is a bug/issue.

Best wishes


So in this case until somebody will fix this… Use only Avast or only CIS… On Avast forum you can find topics about Comodo Firewall 6 and Avast AV 8 problem as well.

Thanks for the info mate. Hope Avast and Comodo resolve these issues as soon as possible. :slight_smile: