Avast Blocking FileZilla: What It Means and 4 Ways to Fix It

While FTP (File Transfer Protocol) isn’t as popular as it used to be with the rise of platforms such as Dropbox or Google Drive, FileZilla remains one of the most popular FTP client software around.

It’s a convenient way to bulk upload files to a server for a client to download, which many have come to rely on in their workflow.

However, some users of FileZilla have reported instances of Avast Free Antivirus blocking FileZilla, usually during the initial install process.

If this is happening to you, then you’re in the right place. We’re going to explain why this happens and how to go about fixing it.

Why is Avast blocking FileZilla?

It depends on whether your Avast software is blocking FileZilla during initial installation or during file transfer.

If during installation there is some in-built, third-party offer software bundled in with FileZilla, that has a high likelihood of triggering Avast’s antivirus detection and needs to be dealt with.

Alternatively, if Avast Firewall intercepts data transfer between your local computer and the target server due to believing it’s a suspicious action, you will need to head into the Avast settings and instruct Avast firewall to allow this process.


When you download and run the FileZilla installer, you are also unknowingly downloading another piece of software called FusionCore, which is a bundler that packs in offers and additional software you can install while you install FileZilla.

A very common example of this is placing a tick box somewhere during installation (that’s ticked automatically unless you specifically spot it and untick it) that will install something like a new web browser on your machine.

While FusionCore is not malicious in nature (although ads and unwanted software you have to go and manually remove is frustrating) it will very often get picked up by Avast, as its behavior and the fact that it’s baked into the FileZilla installer can appear suspicious.

Ads and offers

In addition to the FusionCore bundler itself, many of these packed-in ads and offers also require communication to that particular provider’s website in order to populate the data/image/text used within the ad.

For example, if FileZilla were bundled with an Opera browser ad through FusionCore, that ad communicates with the Opera website/datacenter to retrieve the information it needs to display the ad.

This is where Avast Firewall will often kick in, blocking the FileZilla installation because it’s deemed that data transfer between the installer and the advertisements datacenter to be dangerous.

Data transfer

If you are already past the installation stage and your Avast software is blocking the process of uploading a file to a particular server, it may be that Avast has flagged either the process or the target server as unsafe and has intercepted the data transfer.

In this scenario, another exception may need to be added to the Avast Firewall to mark the file destination as safe.

How to stop Avast from blocking FileZilla

Now we know the sources that can potentially trigger Avast to begin blocking Filezilla: the FusionCore bundler, data transfer between ads and their corresponding servers, and legitimate data transfer that Avast Firewall intercepts. We can now go about fixing them.

For any blockages that occur during the installation process, we can use exceptions within the Avast Antivirus to allow this process through. For issues relating to data transfer blockages, we can use rules within the firewall to instruct it to not intercept legitimate data transfers.

Add a virus exception within Avast

Adding an exception within the Avast free antivirus software will whitelist the files and instruct it to ignore a given executable file. Of course, this should only be performed when you are 100% sure the file in question doesn’t present a threat.

With that being said, FileZilla is very well known and considered common software, and we are also aware that FusionCore is prone to be flagged as a false positive.

Because of this, we can quite confidently bypass the antivirus check here without worrying about letting anything malicious into our machine.

Please do remember to download the installer from the official FileZilla website so you can be sure it’s a legitimate copy.

Here’s how to add the file exception within Avast:

  1. Open the Avast software and navigate to settings.
  2. Click the General tab at the top, and then the Exceptions tab.
  3. Click the “Add advanced exception,” which is the white text next to the green “Add exception” button.
  4. We can then use the advanced exception to select the FileZilla installer. You shouldn’t need to select Fusioncore as a separate process, as it’s basically still a part of the installer.

Once this exception has been added, FileZilla or any bundled processes will no longer be scanned by Avast, meaning you can do a full system scan without issue.

Add a firewall exception

You may ask yourself why we also need to allow FileZilla through the firewall if we’ve just added an exception within the antivirus.

This is because even when FusionCore is active and displaying an ad, that ad needs to pull elements from the corresponding company’s data center in order to display the advertisement to you.

This is a different process than an executable file, and if the firewall suspects it as a malicious process, it will be blocked.

To add a new firewall rule, follow these steps:

  1. Within the Avast GUI, navigate to Protection and then Firewall.
  2. Click the settings icon in the top right, indicated by a small gear icon.
  3. Click “View firewall rules.”

Here, we can add a new rule to exclude internet traffic used by the FileZilla installer.

This will help you get FileZilla installed, but you may find that even after it’s installed, it may try to interrupt your personal file uploads because this is technically a different process than the FusionCore data transfers that occur during install.

Simply repeat the steps mentioned above, but this time exclude the FileZilla executable file that’s installed on your machine.

Additional download options

While the virus and firewall exceptions should fix the large majority of issues, something users have reported on the Avast forums is that picking a download from the “Additional download options” area of FileZilla has worked for them.

You can pick the relevant installer for your operating system, and it may very well work without being flagged by Avast at all.

Temporarily disable Avast during install

In this unique scenario, we know the FileZilla is trusted software and does not need to be monitored by Avast. Therefore, if it is blocking FileZilla during installation, you can simply disable Avast for a bit while you install the software.

As the FusionCore process is only active during the installation of the software, once Filezilla has been restored, we can then re-enable Avast and have it monitor as normal.

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