Are Firewalls Still Relevant When You Have Endpoint Detection and Response (EDR)?
If you’ve recently invested in an Endpoint Detection and Response (EDR) solution, you might be asking yourself: do we still need a firewall? It’s a fair question — and one we hear often from IT managers and business owners trying to rationalize their security stack. The short answer is yes, absolutely. But understanding why will help you make smarter decisions about your cybersecurity investments.
In this article, we’ll break down exactly what firewalls and EDR do, where each one falls short on its own, and why the most resilient organizations use both — together.
The Quick Answer: Firewalls and EDR Solve Different Problems
Think of your cybersecurity like a modern bank. A firewall is the vault door and the security guard at the entrance — it controls who and what gets in or out. EDR is the network of cameras and motion sensors inside the bank — it monitors behavior once someone is already inside.
Remove either one and you have a meaningful gap. A bank without a front-door guard is easy to enter. A bank without interior cameras can’t catch the insider threat that already walked through security. You need both.
What Does a Firewall Actually Do?
A firewall operates at the network level, inspecting traffic as it moves in and out of your environment. Modern next-generation firewalls (NGFWs) go far beyond simple port-and-protocol filtering. Here’s what they provide:
- Network perimeter control: Firewalls act as gatekeepers at the edge of your network. Before a packet of data even reaches a device, the firewall decides whether it should be allowed in at all.
- Blocking known malicious traffic: Firewalls equipped with threat intelligence feeds block connections to known malware command-and-control (C2) servers, malicious IP addresses, and dangerous domains — proactively, before any endpoint is touched.
- Preventing lateral movement: Once a threat is inside a network, firewalls with segmentation capabilities can limit how far it can spread. This is critical for containing ransomware before it encrypts your entire environment.
- Enforcing network policies: Firewalls ensure that only approved applications and protocols communicate in and out of your network — reducing your attack surface significantly.
- Visibility into network traffic: NGFWs provide logs and analytics on what’s traversing your network, helping security teams identify anomalies at a macro level.
What Does EDR Do — and Why Is It Not Enough Alone?
EDR solutions monitor activity on individual endpoints — laptops, desktops, servers, and mobile devices — to detect and respond to threats that have already reached those devices. Key EDR capabilities include:
- Behavioral monitoring: EDR watches how processes behave on an endpoint in real time. If a Word document suddenly starts spawning command-line processes — a classic sign of a macro-based attack — EDR detects and flags it.
- Fileless attack detection: Many modern attacks never write a file to disk, making traditional antivirus blind. EDR detects these in-memory attacks based on behavior, not signatures.
- Threat hunting and forensics: EDR records a rich timeline of endpoint activity, enabling security teams to investigate how an attack unfolded and what data may have been accessed.
- Automated response: Modern EDR platforms can automatically isolate a compromised endpoint from the network, kill malicious processes, and roll back changes — containing damage in real time.
So what can’t EDR do? It cannot stop malicious traffic at the network edge before it arrives at an endpoint. It cannot prevent data exfiltration through an unchecked network connection. And it provides no protection for IoT devices, network printers, or other non-endpoint assets that don’t support an EDR agent.
The Dangerous Gaps Created When You Rely on Only One
Firewall Only — Without EDR:
- Advanced threats that arrive via legitimate channels (phishing emails, USB drives, compromised SaaS applications) bypass the firewall entirely.
- Fileless malware and living-off-the-land techniques operate entirely within trusted processes — invisible to network-level controls.
- Once inside, an attacker can move laterally and escalate privileges with little visibility or resistance.
EDR Only — Without a Firewall:
- Your network has no perimeter defense. Inbound attacks from the internet hit your endpoints directly, giving EDR less time to react.
- Known malicious IP addresses and command-and-control servers are never blocked — EDR must catch the resulting behavior after the connection is already made.
- Network-level attacks targeting routers, switches, IoT devices, or unmanaged assets have zero protection.
- Without network segmentation enforced by a firewall, a single compromised endpoint can communicate freely with every other device on the network.
How Firewalls and EDR Work Together: A Layered Defense
The cybersecurity industry has long endorsed a defense-in-depth approach — the idea that no single control is sufficient, and layers of protection dramatically reduce your overall risk. Firewalls and EDR are purpose-built to complement each other at different layers:
- Layer 1 — Before the threat arrives: The firewall blocks known malicious traffic, enforces network policies, and reduces the volume of threats that even reach your endpoints.
- Layer 2 — As the threat tries to execute: EDR monitors endpoint behavior in real time. Even if something slips past the firewall (via email, a browser exploit, or a supply chain compromise), EDR detects the malicious activity and responds.
- Layer 3 — After the threat executes: Both tools provide logs, alerts, and forensic data. The firewall reveals unusual outbound connections; EDR reveals what happened on the endpoint. Together, they tell the full story of an attack — essential for incident response and compliance reporting.
A Real-World Attack Scenario: What Happens Without Both?
Consider this common ransomware attack chain:
Step 1: An employee clicks a phishing link and unknowingly downloads a dropper. The firewall didn’t block it because the domain was newly registered and not yet on any threat intel feed.
Step 2: The dropper attempts to contact a command-and-control server. The firewall, with an updated threat intelligence feed, blocks the outbound connection. The attack stalls.
Without the firewall: The C2 connection succeeds. The attacker receives the beacon, deploys the ransomware payload, and begins encrypting files. EDR detects the encryption behavior — but by the time it isolates the endpoint, dozens of files are already gone.
Without the EDR: Even if the firewall blocks C2, a variant that uses legitimate cloud services (like Google Drive or Dropbox) as a relay successfully phones home. No behavioral detection means the attacker has free rein on the endpoint.
With both: The firewall provides the first line of resistance; EDR catches what gets through. The attack is detected and contained before business impact.
Compliance and Cyber Insurance: Both Are Often Required
If your business operates under any regulatory framework — PCI-DSS, HIPAA, SOC 2, NIST, or ISO 27001 — a firewall is almost certainly a mandated control, not an optional one. These frameworks were designed with defense-in-depth in mind and expect network-level controls to be in place regardless of what endpoint tooling you deploy.
Similarly, cyber insurance providers have become increasingly specific about the security controls they require for coverage. Many insurers now require documented evidence of both network perimeter controls and endpoint detection capabilities before issuing or renewing a policy. Dropping your firewall to “save money” can put your entire policy at risk.
Frequently Asked Questions
Can EDR replace a firewall for small businesses?
No. EDR protects managed endpoints; firewalls protect the network. Small businesses are actually higher-risk targets precisely because they often lack layered defenses. Affordable next-generation firewall options exist that are purpose-built for SMBs and require minimal management overhead.
We’re fully in the cloud — do we still need a firewall?
Yes. Cloud environments have their own firewall equivalents — security groups, cloud-native WAFs, and network access controls. The concept of network-level perimeter defense doesn’t disappear in the cloud; it shifts to cloud-native tools. EDR still protects the endpoints (virtual machines, containers, or employee workstations) accessing those cloud environments.
Is a firewall alone enough if I can’t afford EDR?
A firewall provides meaningful protection and is a great foundation, but modern threats are sophisticated enough that endpoint-level visibility is increasingly critical. Many EDR solutions now offer budget-friendly tiers for small businesses. A managed security provider can often deliver both firewall management and EDR monitoring as a bundled service at a cost-effective price point.
What’s the difference between EDR and traditional antivirus?
Traditional antivirus relies on signature-based detection — it looks for known malware fingerprints. EDR uses behavioral analysis to detect unknown threats by identifying suspicious activity patterns. EDR is not a replacement for AV — it’s a significant advancement. Many modern endpoint security platforms bundle both capabilities.
The Bottom Line: Don’t Choose One Over the Other
Firewalls are not a legacy technology being replaced by EDR. They are fundamentally different tools solving fundamentally different problems at different points in the attack chain. The organizations that suffer the most damaging breaches are rarely those that lack the most sophisticated tools — they’re the ones that have gaps in their layered defenses.
The question isn’t “firewall or EDR?” — it’s “how do we make our firewall and EDR work together as effectively as possible?”
Ready to assess your current security posture? Our team of cybersecurity specialists can evaluate how your firewall and EDR solutions work together — and identify any gaps that could leave you exposed. Contact us today for a security review.
About the Author: This article was written by the cybersecurity team at ANC Systems. We specialize in helping businesses of all sizes build layered, practical security programs that keep threats out and minimize damage when they get through.