You Really Shouldn

Custom Windows ISOs have been earning a lot of attention online recently, with many singing the praises of these tweaked and customized distributions for everything from improving privacy, reducing telemetry and improving performance both generally and in games. But don’t be fooled, Windows ISOs are not the same as their distro cousins on Linux, and can be a serious security threat.

Luckily, there are some great alternative tools that can help you achieve the same bloat-free, speedy OS, without the risks.

What are custom ISOs?

Custom ISOs are modified and repackaged versions of Windows

Custom images for Windows have been around almost as long as Windows has, and indeed for any other software packaged as images. There’s a whole ecosystem of tools that allows you to download a Microsoft distributed image for Windows – the .iso files you download and burn onto a USB stick or CD. Before installing these images, you can open and modify them, adding features, installing software or making tweaks to Windows for a variety of reasons.

There are plenty of users online who are modifying and making these custom images for a range of purposes, then providing them for download. This can be anything from removing bloatware, improving gaming performance or disabling tracking cookies, but there are more nefarious reasons as well.

Why are custom ISOs dangerous?

There’s no telling what could have been modified in an ISO

Source: TechLatest

Custom Windows ISOs are fundamentally, extremely dangerous, and you shouldn’t use them. This is largely because there’s no easy way to tell what elements of an ISO have been modified (without inspecting it against a valid ISO yourself – a difficult process). This means that once installed, your PC could immediately become a part of a botnet, have a malicious rootkit installed, or any number of other dangerous.

You also sacrifice any other protections you have by providing a potentially malicious attacker root access to your filesystem before you even install it. This could include any number of threats, like adding malicious certificates and performing man-in-the-middle traffic sniffing attacks, as well as disabling any protection you might have – like your antivirus or firewall.

Signed ISOs are much safer

You may discerningly ask – how are Linux ISOs safe? The key element that keeps Linux ISOs safe is the checksum that accompanies them. This checksum is generated in combination with a PGP (normally) keypair, which allows the developers of a distro to publicly verify that they are who they say they are. This is known as software signing, and installing unsigned software is likely to cause a set of “We can’t verify the developer of this software” warnings in your OS.

These distros are also open-sourced, allowing the public to verify that the contents of an ISO are what they’d expect.

All of this does rely on your trusting the original developers of the distro, and this has been a problem for Linux distros before, so there’s no guarantee of safety, but these steps help mitigate risk and prompt community verification.

What should I use instead?

Post-install modification is a far better idea

There are plenty of great alternatives to downloading a custom Windows ISO. The best of these is to use some kind of post-install script which runs locally on your PC. These scripts are open-source, so their contents can be verified by the community, and shouldn’t download any binaries directly – another vector of potential compromise.

There are some great examples of scripts for various things that can improve your Windows experience in the same ways as custom ISOs, but with significantly less risk. As with any potentially dangerous modifications to your operating system like this, though, caution should be exercised. We’d encourage everyone to validate the scripts themselves, and only use scripts from reputable sources.

Here are a few useful examples:

Win11 Debloat

Win11Debloat is a simple powershell script that does what it says on the tin – removes a lot of bloat from your Windows OS. Some of the benefits here include disabling telemetry, removing default apps, nuking Bing and Copilot out of existence and much more. You can check the script out on GitHub.

ChrisTitusTech’s WinUtil

This one is technically a script, but is pushing the boundaries a bit. It’s got a fully functional GUI, and a range of tweaks, tools, updates and config options. It’s a complete one-stop-shop for optimizing your Windows install for debloat and speed. There aren’t too many crazy gaming tweaks here, but there are nice pre-configured options for security and updates.

This also has the benefit of being super easy to get started with, and very approachable (due to its GUI). There’s also no need to download the script – it can be run with a one-liner from your Powershell terminal – though this isn’t necessarily the safest thing to do if you’re the cautious type.

You can check out WinUtil on GitHub.

You can always build your own

In all of this, it’s important to make a distinction. Custom Windows images are only dangerous because you can’t trust the person building them – there’s no harm in building your own. It’s even something that’s been covered on XDA previously. Nothing is also stopping you making use of some of the tools above and bundling the image yourself, before burning it to a USB or similar for repeat installs across all of your PCs.

Closed-source unverified distros are dangerous

Fundamentally, closed-source Windows distros are dangerous, and you should steer clear. There are plenty of examples out there – which we’ve avoided linking to specifically – but however reputable the developer looks, the lack of easy verification of their contents makes these distros fundamentally dangerous. If you’re downloading Windows (or any other OS for that matter) you should only use the first-party supplied site.

The kind of exploits that can live in these distros can lie undetected for years, and you may never even notice they’re there. It’s important to protect your home cybersecurity, as the consequences can be disastrous, and potentially life-changing.