For twenty years, antivirus was the answer to the question "how do we protect our computers?" You installed it, it scanned files, it caught known viruses, and that was largely that. Then attacks changed, and the old model started missing things that mattered. EDR is what the industry moved to in response. This is the plain-English version of what is different, why traditional antivirus is no longer enough on its own, and what the change means for a normal UK business.
What antivirus actually does
Traditional antivirus works mainly by recognition. It keeps a list of known-bad files, called signatures, and checks the files on your computer against that list. If something matches, it gets blocked or quarantined. It is fast, it is cheap, and for the kind of mass-market viruses that dominated the early internet it worked well, because the same malicious file was sent to millions of machines and a signature for it protected everyone.
The weakness is in that word: known. Antivirus is good at things it has seen before and poor at things it has not. An attacker who changes a single byte of a file, or who uses a brand-new piece of malware, can sail past a signature check because there is no matching entry on the list yet. Modern attackers automate exactly that, generating endless unique variants, which is why pure signature matching slowly stopped being enough.
What EDR adds on top
EDR stands for Endpoint Detection and Response, and the clue is in the second half. Rather than only asking "is this file on my bad list?", EDR watches what is actually happening on the machine: which programs run, what they touch, what they try to talk to over the network, whether one process suddenly starts encrypting hundreds of documents. It looks at behaviour, not just identity.
That shift matters because bad behaviour is harder to disguise than a bad file. An attacker can rename a tool, but they cannot easily hide the fact that a Word document just launched a script that started copying data out of the business. The "response" half is the other half of the value: when EDR spots something wrong, it can isolate the machine from the network, kill the process and give your security team a timeline of exactly what happened, so they can act in minutes rather than discovering it weeks later.
- •Antivirus asks: is this a known-bad file?
- •EDR asks: is this program behaving like an attack, whether we have seen it before or not?
- •EDR records activity so an incident can be investigated and contained, not just blocked
- •Modern EDR usually includes the antivirus layer too, rather than replacing it outright
Where MDR and XDR fit in
You will hear two more acronyms in the same breath, and they cause a lot of confusion, so here they are in one line each. MDR, Managed Detection and Response, is EDR with humans attached: a specialist team watches your alerts around the clock and responds on your behalf, which matters because EDR generates alerts that someone competent has to act on at 3am. XDR, Extended Detection and Response, simply widens the lens beyond the endpoint to also take in email, identity and cloud signals, so a single attack that touches several systems is seen as one story rather than several disconnected warnings.
For most UK SMEs the practical answer is EDR delivered as a managed service, because buying the tool is the easy part and staffing the response is the hard part. We go deeper on choosing between providers and tiers in how to choose an EDR platform, and our managed detection and response service is the staffed version of exactly this.
Does this mean antivirus is dead?
Not quite, and it is worth being precise. The signature-based scanning that defined old antivirus has not disappeared; it has been absorbed. A modern endpoint product still blocks known-bad files cheaply and instantly, because there is no reason to investigate the behaviour of something you can already recognise as malicious. What has died is the idea that signature scanning on its own is adequate protection.
So the honest framing is not "EDR instead of antivirus" but "antivirus as one layer inside a tool that also watches behaviour and can respond". If your business is still running a standalone, signature-only product bought years ago, that is the gap worth closing. Cyber insurers and frameworks like Cyber Essentials increasingly expect the behavioural, response-capable layer to be present, not just a basic scanner.
What this means for your business
If you are a small business that has never been told any of this, the takeaway is simple: the protection most people picture when they say "antivirus" is no longer the whole job. The attacks that actually hurt UK businesses, ransomware in particular, behave in ways that behavioural detection is designed to catch and signature scanning is not.
The move from legacy antivirus to EDR is one of the highest-value security upgrades a typical organisation can make, and it is usually less disruptive than people fear. If you want the detailed migration view, including how to run old and new tools side by side during a switch, see migrating from legacy AV to EDR, and our endpoint security service covers deployment end to end.