If you're reviewing your IT costs, the antivirus subscription is an obvious line to question. Windows already comes with Microsoft Defender, so why pay for something else? It's a fair question, and the honest answer is that it depends on what you have, what you need, and who is watching it.
Let's untangle the options in plain English.
First, which "Defender" are we talking about?
Microsoft uses the Defender name for several different products, which causes a lot of confusion. The two that matter most for a small organisation are:
- **Microsoft Defender Antivirus**: the free protection built into Windows 10 and Windows 11. It scans files, blocks known malware and updates itself automatically. For a single home PC, it's genuinely decent.
- **Microsoft Defender for Business**: a business-grade endpoint security product. It's included in Microsoft 365 Business Premium and can also be bought on its own. It builds on the built-in antivirus and adds central management and more advanced detection.
So when people search "Microsoft Defender for Business vs antivirus", they're often comparing something more capable than they realise.
What the free built-in antivirus does, and doesn't, do
The built-in antivirus is a solid baseline. It will catch a lot of common threats and it costs nothing extra. The limitations show up when you have more than a handful of computers:
- There's no single dashboard showing the health of every device in your office.
- Nobody is alerted if a laptop has stopped updating or protection has been switched off.
- It's focused on spotting known bad files, rather than suspicious behaviour, such as an attacker using legitimate tools to move around your network.
- There's no central record to help you understand what happened after an incident.
In short, each PC is protecting itself, but nobody is looking at the whole picture.
What Defender for Business adds
Defender for Business is designed to close those gaps. Key features include:
- **Endpoint detection and response (EDR)**: it watches for suspicious behaviour, not just known malware, which matters because many modern attacks, including ransomware, don't rely on a single obvious virus file.
- **Automated investigation and response**: it can isolate a device or remediate a threat automatically.
- **Attack surface reduction**: rules that block risky behaviours, such as Office documents launching unexpected programs.
- **Vulnerability management**: highlighting devices with missing updates or risky software.
- **Central management**: policies and alerts managed from one portal, covering Windows, Mac and mobile devices.
If you already pay for Microsoft 365 Business Premium, you may well have this already and not be using it. That's one of the most common things we find when we look at a business's setup.
So where do paid third-party products fit?
There are many well-regarded endpoint protection products from other security vendors, and some offer excellent detection, reporting and support. Reasons an organisation might choose one include:
- You're not on a Microsoft 365 plan that includes Defender for Business.
- You need a particular feature, integration or compliance reporting.
- Your IT provider uses a specific platform to monitor all their clients consistently.
- You want a bundled service that includes a security team watching alerts around the clock (often called managed detection and response, or MDR).
There isn't a single "best" product. Independent testing generally shows the major business products, including Microsoft's, performing well. The differences tend to be in management, reporting and support rather than raw detection.
The question that matters more than the brand
Here's the part that often gets missed: **any security tool is only as good as the response to its alerts.**
A top-tier product that flags a suspicious login at 2am does very little if the alert lands in an inbox nobody checks. Equally, protection that has quietly been disabled on one laptop leaves a door open, however good the software is.
So instead of asking "Defender or paid antivirus?", it's more useful to ask:
- Is every device actually covered and up to date?
- Who receives alerts, and how quickly do they act?
- Are the advanced features switched on and configured properly?
- Is this backed up by other layers, such as multi-factor authentication, email filtering, patching and reliable cloud backup?
Endpoint protection is one layer. On its own, it won't stop someone who has phished a password and logs in to your email from anywhere in the world.
Our practical advice
For most small businesses, schools and charities:
- **Don't rely on the free built-in antivirus alone** once you have several devices and sensitive data to look after.
- **Check what you're already paying for.** If you have Microsoft 365 Business Premium, Defender for Business may be sitting there unused, and you might be able to drop a separate antivirus licence.
- **Make sure someone is monitoring it.** Whether that's an in-house person or a managed IT provider, alerts need a human who understands them.
- **Think in layers**, with backup as your safety net if everything else fails.
Not sure what you've got?
If you'd like a clear picture of how well your devices are really protected, and whether you're paying twice for the same thing, we'd be happy to help. Cloud 4 Sure offers a free IT health check for organisations across Sussex, Surrey, Hampshire and Kent. Get in touch and we'll take a look, with straightforward advice and no jargon.