Antivirus stops known malware. It does not stop an attacker already inside your network from using stolen credentials. That gap is why UK agencies with 70 to 150 people are moving from basic endpoint protection to managed detection and response (MDR). Endpoint protection watches individual devices. MDR adds a human team that watches, investigates, and acts on what those devices report, around the clock.
For a growing agency, this is not a theoretical upgrade. It is the difference between a threat being caught in minutes and a threat sitting undetected for days while it moves through client files, finance systems, and shared drives.
Agencies at this size sit in an awkward gap. They hold enough valuable data, client contracts, financial records, and campaign assets to be worth attacking, but rarely have the headcount to run their own around-the-clock security team. Buying a well-reviewed antivirus product feels like ticking the box. In practice, it only covers the threats security researchers already know about.
Antivirus, EDR, and MDR are three different layers, not three names for the same thing
Traditional antivirus checks files against a list of known threats. It works well against malware it already recognises and does almost nothing against an attack it has never seen before.
Endpoint detection and response, or EDR, goes further. It watches behaviour on each device in real time, flagging anything unusual rather than only known bad files. But EDR still needs someone to read the alerts and decide what to do.
MDR is EDR plus a team of analysts who do exactly that. In Dr Logic’s experience, this is the layer most 70-150 user agencies are missing. They have deployed a modern tool, but nobody is watching it at 2 am on a Saturday when an alert actually matters.
Each layer solves a different part of the problem, and none of them replaces the others. Antivirus still catches the bulk of everyday, low-sophistication threats efficiently and cheaply. EDR catches the behaviour that antivirus cannot see. MDR ensures a person actually reviews and acts on what EDR flags, rather than the alert sitting in a queue until someone happens to check it. Removing any one layer leaves a specific, predictable gap rather than a general weakness.
Fileless attacks are why signature-based antivirus keeps missing modern threats
Many of today’s most damaging attacks never write a traditional file to disk at all. Attackers use legitimate tools already installed on the machine, such as PowerShell or scripting utilities, to carry out the attack. Security teams call this living-off-the-land.
Traditional antivirus has nothing to scan, because there is no malicious file to catch. The activity looks like normal admin work until the behaviour itself gives it away. This is precisely the kind of activity that behaviour-based EDR is built to spot, and that an MDR team is trained to investigate before it escalates.
For a design or marketing agency handling client assets, financial data, and shared credentials across dozens of devices, this blind spot is a genuine business risk, not an edge case. A stolen login used outside normal hours, or a script quietly copying files to an external location, looks routine to a tool that only checks file signatures. It looks very different to a system, or a person, trained to spot behaviour that does not match how that account or device usually acts.
This is also why deploying EDR alone is only half the answer. The tool can flag the unusual behaviour correctly and still achieve nothing if the resulting alert waits unread in a dashboard over a weekend. The detection did its job. The response did not happen.
A 100-person agency does need monitored response, not just monitored alerts
Cost is the first question most agency leaders ask, and it is a fair one. MDR costs more than antivirus alone. But the comparison that matters is not tool against tool. It is the cost of a monitored response against the cost of a breach that runs undetected over a weekend.
Three factors decide whether MDR is the right next step for an agency this size:
- Confirm whether anyone on the internal team is actively watching security alerts outside office hours.
- Check how quickly a real alert would reach a person who can act on it, not just a dashboard nobody is watching.
- Review whether the business holds client data, financial records, or credentials valuable enough to be a deliberate target rather than a random one.
If the answer to any of these points to a gap, MDR closes it without requiring the agency to hire and staff a security team of its own.
Endpoint protection vs MDR: How the layers compare
| Capability | Traditional antivirus | EDR | MDR |
|---|---|---|---|
| Detects known malware | Yes | Yes | Yes |
| Detects fileless and behaviour-based attacks | No | Yes | Yes |
| Generates real-time alerts | Limited | Yes | Yes |
| Human-monitored investigation | No | No | Yes |
| Active response to confirmed threats | No | Manual | Yes, managed |
| Suited to a 70- 150-user agency with no in-house SOC | Insufficient alone | Partial | Best fit |
The Dr Logic team recommends MDR as the baseline for any agency of this size that does not already run its own 24/7 security operation. EDR without monitoring still leaves the same gap that antivirus does: an alert nobody reads is no better than no alert at all.
What this means for a growing agency’s IT budget
Moving to MDR does not usually mean replacing existing tools. Most MDR services layer onto EDR already installed on company devices, adding the monitoring and response element rather than starting from zero. For agencies already running Apple fleets managed through a device management platform, this sits alongside existing device policy rather than competing with it.
The practical next step for most agencies at this size is a short review of current endpoint coverage before committing to a full MDR service, so budget goes toward closing an actual gap rather than duplicating protection that is already in place.
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FAQs
What is the difference between antivirus, EDR, and MDR?
Antivirus blocks known malicious files. EDR monitors device behaviour to catch threats antivirus misses, including attacks with no file involved. MDR adds a human team that watches EDR alerts around the clock and acts on genuine threats. Most agencies need all three layered together, not one in isolation.
Do we really need 24/7 monitored response at our size?
If nobody on your team is actively reviewing security alerts outside office hours, the answer is usually yes. Attacks do not wait for business hours, and an alert that sits unread over a weekend gives an attacker days of unmonitored access to client and financial data.
Is MDR expensive compared to standard antivirus?
MDR costs more than antivirus alone because it includes ongoing human monitoring, not just software. For most 70-150 user agencies, this cost sits well below the cost of a breach going undetected for days, particularly where client data or financial systems are involved.
Can we add MDR without replacing our existing security tools?
In most cases, yes. MDR services typically layer onto EDR software already installed on company devices, adding monitoring and response rather than replacing what is already there. A short review of current coverage identifies exactly what needs adding.
Does MDR replace the need for a SOC or SIEM?
No. MDR, SOC, and SIEM solve related but distinct problems. SIEM collects and analyses security data. A SOC provides the people and process to act on it. MDR is a managed service that typically bundles endpoint-focused detection with that same monitored response, tailored to devices rather than the whole IT estate.
