What Is Endpoint Detection and Response (EDR)?

Why Traditional Antivirus Is No Longer Enough

Traditional antivirus detects threats by matching files against a database of known malicious signatures. This approach was adequate when malware was relatively static and signature databases were comprehensive. Modern attacks have invalidated this model. Ransomware operators use custom malware, obfuscated code, and "living off the land" techniques, using legitimate Windows tools like PowerShell, WMI, and PsExec to conduct attacks without introducing any malicious files at all. A signature-based scanner cannot detect an attack conducted entirely with legitimate tools.

How EDR Works

Endpoint Detection and Response (EDR) takes a fundamentally different approach. Rather than looking for known malicious files, EDR monitors endpoint behavior, what processes are running, what network connections are being made, what files are being accessed, what commands are being executed, and uses behavioral analysis to identify suspicious patterns. An EDR solution can detect that a legitimate Excel process is spawning a PowerShell command that is downloading and executing code from the internet, even if the specific malware being downloaded has never been seen before.

EDR vs. Antivirus vs. XDR

• Antivirus: Signature-based detection of known malware. Insufficient against modern attacks. Still necessary but not sufficient.
• EDR: Behavioral detection and active response on endpoints. Provides visibility into attack techniques that antivirus misses.
• XDR (Extended Detection and Response): Extends EDR to also cover network, cloud, and identity telemetry. Provides broader visibility across the entire environment.

EDR in the Context of Penetration Testing

EDR solutions are a significant obstacle to penetration testers, which is precisely the point. Grid32 engineers test whether your EDR solution is configured to detect the techniques attackers actually use. A common finding is EDR deployed but not in blocking mode, or configured with too many exclusions that create gaps attackers can exploit. A penetration test validates whether your EDR deployment is actually providing the protection it was purchased to deliver.

EDR Is Not Set and Forget

Deploying EDR is the beginning, not the end. Its value depends on tuning, coverage, and response: agents must be on every endpoint, alerts must reach someone who acts on them, and detection rules need adjustment as attacker techniques evolve. An EDR left in default mode with no one watching the console provides far less protection than its license suggests. A penetration test measures whether your EDR actually detects and slows a realistic attack, and how quickly your team responds when it fires.

Frequently Asked Questions

What is EDR (endpoint detection and response)?

EDR is security software on endpoints that continuously monitors behavior, detects suspicious activity, and lets responders investigate and contain threats. Unlike traditional antivirus, it focuses on attacker behavior rather than known malware signatures alone.

How is EDR different from antivirus and XDR?

Antivirus blocks known malware by signature, EDR detects and responds to attacker behavior on endpoints, and XDR extends that correlation across email, network, identity, and cloud. EDR is the endpoint-focused layer of modern detection and response.

How does penetration testing relate to EDR?

A penetration test measures whether your EDR actually detects and slows a realistic attack, including how quickly your team responds. It reveals detection gaps and misconfigurations that only show up under genuine adversarial pressure.