What is EDR and XDR: threat detection and response in depth

Why traditional antivirus isn't enough anymore

Classic antivirus (AV) relies on signature-based detection — it keeps a database of fingerprints (hashes) of known malware and checks every file that runs or gets saved against it. If the hash matches an entry in the database, the file gets blocked or removed. This approach worked well in an era when the same virus spread unchanged across thousands of victims.

The problem is that today's malware easily evades this model. Polymorphic and metamorphic malware changes its code on every infection, so each copy has a different hash. Fileless malware doesn't write to disk at all — it runs directly in memory using legitimate tools like PowerShell, WMI, or Office macros, so there's nothing to match against a signature database. And an attacker who's already inside the network using stolen credentials isn't using any malware at all — just legitimate tools and legitimate permissions, which looks completely innocent to AV.

Signature-based AV is comparable to a doorman who recognizes known thieves from photographs — if the thief puts on a mask or sends someone the doorman doesn't recognize, they walk right in. That's exactly the gap EDR fills.

What EDR is

EDR (Endpoint Detection and Response) is a category of security tools that, unlike antivirus, don't wait for a match against a known pattern — instead they continuously record and analyze behavior on endpoints: laptops, servers, virtual machines, and mobile devices. Instead of asking "do I recognize this file as malicious?", EDR asks "does this behavior look suspicious, regardless of which tool caused it?".

The term was coined in 2013 by Gartner analyst Anton Chuvakin under the original name Endpoint Threat Detection and Response (ETDR), later shortened to EDR. The category emerged as a direct response to the limits of the signature-based approach described above — security teams needed visibility into what was actually happening on endpoints, not just a binary "allow / block" decision at file execution.

EDR rests on four pillars that together form a closed loop:

• Continuous telemetry recording — the endpoint agent collects data on processes, network connections, the file system, the registry, and memory, regardless of whether an attack is happening right now.
• Detection — behavioral analysis, heuristics, and machine learning evaluate the collected telemetry and look for patterns matching known and unknown attack techniques.
• Threat hunting — security analysts can actively search historical telemetry for traces of an attacker who hasn't triggered any automatic alert yet.
• Response — once a threat is confirmed, EDR enables direct intervention: isolating the device, killing a process, quarantining a file, or rolling back changes.

How EDR works technically

A lightweight software agent runs on every monitored device and integrates deeply into the operating system — on Windows typically through a kernel-mode driver or ETW (Event Tracing for Windows), on macOS and Linux through equivalent system interfaces. The agent continuously records events such as:

• Process creation and termination — including the full parent-child chain (e.g. Word launched PowerShell, which launched another process — an unusual and suspicious sequence).
• Network connections initiated from the endpoint — destination IP address, port, domain.
• File system changes — creating, modifying, encrypting, or deleting files at high volume (a typical ransomware indicator).
• Registry changes (Windows) — especially writes to keys tied to automatic startup, a common persistence technique.
• Memory access — techniques like process injection or credential dumping (e.g. an attempt to read passwords out of the lsass.exe process memory).

This telemetry is sent in real time (or near real time) to a central — today almost exclusively cloud-based — analytics engine. That's where correlation happens: a single event on its own often means nothing (launching PowerShell is a common, legitimate operation), but a sequence of events can reveal an attack — for example a phishing attachment opens Word, Word launches a hidden PowerShell command, that downloads a file from an unknown domain and executes it, and it then starts scanning the local network. Each step individually looks innocent; the chain as a whole matches a known attack technique.

Detection techniques EDR combines

What EDR can do once it finds a threat

The key word in EDR is "Response" — unlike a passive monitoring tool, EDR enables direct intervention:

• Host isolation — the device stays connected to the EDR console, but all other network communication is blocked, preventing lateral movement (the attacker spreading to other devices on the network) or data exfiltration.
• Process termination — immediately stopping a malicious process without restarting the entire device.
• File quarantine — a suspicious file gets moved to isolated storage where it can't be executed, but is preserved for forensic analysis.
• Rollback — especially against ransomware, some EDR solutions can revert encrypted files to their pre-attack state using continuously saved snapshots (shadow copies).
• Remote shell — an analyst gets direct command-line access to the affected device for deeper manual analysis, without needing to be physically present.

This combination of deep visibility and direct control makes EDR a tool not just for detection, but also for forensic reconstruction of an attack — tracing back exactly how the attacker got in, which devices they moved through, and what data they accessed (so-called root cause analysis and timeline reconstruction).

Where standalone EDR hits its limits

EDR significantly advanced threat detection, but it has one structural limitation: it only sees what happens on the endpoints it covers. Modern attacks, however, rarely play out entirely on a single device:

• An attack often starts outside the endpoint — with a phishing email that slips past the email gateway, or a compromised cloud account the attacker logged into with legitimate, but stolen, credentials.
• Lateral movement across the network between multiple devices generates telemetry on multiple EDR agents at once, but without central correlation the security team sees them as separate, seemingly unrelated events.
• Cloud and SaaS applications (see our CASB article) often have no EDR agent at all — the data lives there, but no telemetry from that layer flows into EDR.
• Security teams running several separate tools (email security, network monitoring, EDR, cloud security) face alert fatigue — dozens or hundreds of daily alerts from different consoles with no shared context, causing genuinely important signals to get lost in the noise.

This exact gap — missing correlation across layers beyond the endpoint — is what XDR solves.

What XDR is

XDR (Extended Detection and Response) extends the EDR principle — continuous telemetry recording, behavioral detection, active threat hunting, and direct response — beyond the endpoint. Instead of a single data source, XDR collects and, most importantly, correlates telemetry from multiple layers at once:

• Endpoint — the same telemetry as EDR (processes, files, registry, network from the device's point of view).
• Network — traffic flow, DNS queries, anomalies in communication between network segments.
• Email — phishing attempts, malicious attachments and links caught at the email gateway level.
• Cloud and identity — unusual logins, permission changes, suspicious activity in SaaS apps and cloud consoles (tying in with ZTNA and CASB telemetry).
• Servers and workloads — including containers and cloud virtual machines, not just classic laptop-style endpoints.

The key difference from a company simply running five separate security tools side by side is correlation at the level of a single incident. The XDR engine can recognize that a suspicious email, an unusual login to a cloud app, and an unknown process launching on a laptop ten minutes later aren't three unrelated events in three different consoles, but three steps of the same attack — and generates a single, context-rich grouped alert instead of three isolated ones.

Native XDR vs. hybrid (open) XDR

The market has split into two distinct approaches to where XDR gets its telemetry from:

The choice between them mostly depends on how much a company has already invested in existing security tools from different vendors — a complete swap to a single native stack is costly and risky, but offers the deepest possible correlation.

XDR vs. SIEM vs. SOAR

These three acronyms are often mixed up in practice because they partially overlap, but they solve different problems:

• SIEM (Security Information and Event Management) — centralizes and stores logs from all sources in an organization (not just security ones), primarily for compliance, long-term retention, and manual investigation. It's broad but shallow — it collects almost everything, with minimal built-in context about what's actually a threat.
• XDR — is narrower in scope (security telemetry from endpoints, network, email, and cloud), but deeper — it brings its own detection logic, behavioral analysis, and native correlation across those sources, purpose-built for spotting attacks rather than general-purpose logging.
• SOAR (Security Orchestration, Automation and Response) — doesn't collect its own telemetry or perform detection; instead it automates the response using predefined playbooks (e.g. "if XDR reports phishing, automatically block the sender, isolate the affected endpoint, and open a ticket") across multiple tools at once.

In practice these three categories increasingly work together: XDR detects and correlates, SOAR automates the response based on that, and SIEM serves as long-term storage for audit and compliance. Many vendors today offer XDR with built-in SOAR-like automation capabilities, gradually blurring the lines between the categories.

MITRE ATT&CK: a shared language for detection

MITRE ATT&CK is a publicly available, continuously updated database of tactics and techniques used by real-world attackers — from initial access, through persistence, privilege escalation and lateral movement, to data exfiltration. Quality EDR and XDR solutions map their detections directly to specific ATT&CK techniques (e.g. "T1055 — Process Injection"), which lets security teams:

• Name precisely which technique an attacker used, instead of a vague "suspicious activity".
• Systematically evaluate which techniques their tools cover well and where they have blind spots.
• Share attack knowledge using a shared, vendor-neutral language across the entire industry.

MDR: when a company has no in-house SOC team

EDR and XDR are technologies — but technology alone doesn't generate value without people who evaluate, confirm, and respond to alerts around the clock. Small and mid-sized companies can rarely afford their own 24/7 Security Operations Center (SOC). That's where MDR (Managed Detection and Response) comes in — a service in which an external provider deploys and operates EDR/XDR technology on the customer's behalf, and also provides the human layer: continuous monitoring, alert triage, and direct response in case of a confirmed threat. MDR isn't a replacement for EDR/XDR, but a service built on top of these technologies, for organizations that lack the in-house capacity to run them effectively.

EDR and XDR in the context of modern security architecture

In our series on modern security architecture, EDR and XDR logically complement the tools we've covered before, but they address a different phase of the problem. ZTNA, CASB, and DLP focus primarily on prevention — who's allowed to access which application, what data may leave the organization, which cloud apps are under control. EDR and XDR, by contrast, assume that despite all that prevention, an attacker will sometimes get in, and focus on detection and response after the fact. This combination — prevention at the edges and detection on the inside — matches the principle we described in our SASE article: no single layer of defense is bulletproof, and security is the sum of multiple layers building on each other.

What to look for when choosing a solution

• Breadth of telemetry coverage — how many different sources (endpoint, network, email, cloud, identity) a solution actually covers natively, not just through a shallow integration.
• Quality of correlation logic, not just the volume of data collected — a tool that generates hundreds of uncorrelated alerts a day causes the same alert fatigue problem XDR was meant to solve.
• Speed and scope of automated response — whether the solution can not just report a threat but actually stop it itself (isolation, kill process) without waiting for manual intervention, especially outside business hours.
• Impact on endpoint performance — an agent running continuously on thousands of devices needs to be lightweight enough not to get in the way of users' everyday work.
• Availability of an MDR service from the same vendor or a partner, for companies without the capacity to run their own 24/7 SOC team.

Summary

EDR expanded endpoint protection from simple matching against a signature database to continuous recording and behavioral analysis, backed by the direct ability to intervene — isolating a device, killing a process, or reverting changes caused by ransomware. XDR extended that principle beyond a single endpoint, correlating telemetry across email, network, cloud, and identity into one coherent attack story instead of dozens of isolated alerts in separate consoles. Together with preventive layers like ZTNA, CASB, and DLP, EDR and XDR round out modern security architecture with a final, but critically important layer — quickly detecting and stopping an attacker who got in despite everything else.