# Endpoint Detection and Response
Endpoint Detection and Response (EDR) is a category of security technology designed to give defenders continuous visibility into what is happening on individual devices across an enterprise environment. It exists because perimeter-based security models failed to account for threats that originate inside the network, persist through legitimate processes, or evade signature-based detection entirely. EDR solves the visibility gap: the period between when an attacker gains a foothold and when a defender discovers the intrusion. Without endpoint telemetry collected and analyzed in near real time, that gap can stretch from hours to months. EDR compresses it to minutes by recording process behavior, file activity, network connections, and memory events, then correlating those signals against known attack patterns and anomalous baselines.
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Endpoint Detection and Response is a security platform category that deploys persistent agents on managed devices to collect granular telemetry, stream that data to an analysis engine, and enable both automated and analyst-driven response actions. The term was coined by Gartner analyst Anton Chuvakin in 2013 to describe a then-emerging class of tools that went beyond prevention into continuous monitoring and investigation.
EDR is not antivirus. Traditional antivirus operates on a detect-and-block model using file hash signatures and heuristic rules applied at the point of execution. It produces a binary verdict: allow or block. EDR records everything that happens whether or not a block occurs, building an evidence chain that analysts can query after the fact. EDR is also not a Security Information and Event Management (SIEM) system, although the two are complementary. A SIEM aggregates logs from many sources for correlation and alerting; EDR provides the deep endpoint telemetry that feeds those logs and adds response capability.
Adjacent concepts include:
EDR is not a compliance checkbox. Deploying an agent does not mean an organization is protected. The platform requires tuning, triage resources, and operational processes to produce security value.
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EDR operates through four sequential functions: collection, analysis, detection, and response. Each stage builds on the previous one to create a comprehensive security capability that transforms raw endpoint activity into actionable intelligence.
Collection
A lightweight agent is installed on each managed endpoint, typically as a kernel-level or user-space driver that hooks into operating system event channels. The agent records:
This telemetry is timestamped, normalized, and transmitted to a cloud or on-premises backend. Modern EDR platforms typically collect hundreds of event types and can record thousands of events per second on an active endpoint without significant performance degradation, because agents use ring buffers and asynchronous shipping to minimize impact on the host.
The collection mechanism varies by operating system. Windows agents hook into Event Tracing for Windows (ETW) providers and kernel callbacks. Linux agents tap into auditd, eBPF, or kernel modules. MacOS agents register for Endpoint Security Framework notifications. Mobile EDR, a specialized subset, operates through management API access rather than direct kernel instrumentation due to platform restrictions.
Analysis
The backend applies multiple detection layers simultaneously. Rule-based detections match specific sequences of behavior against known attack patterns, many of which are mapped directly to MITRE ATT&CK techniques and sub-techniques. Machine learning models trained on large corpora of endpoint telemetry flag statistical anomalies, such as a process spawning a child that it has never spawned before, or a binary executing from an unusual path. Threat intelligence feeds add context by identifying known malicious IP addresses, file hashes, domains, and certificate fingerprints.
The analysis engine builds a process tree and timeline for every detection, so that when an alert fires, the analyst does not see an isolated event but rather the full chain of activity that led to it. This contextual approach is crucial because individual events are often ambiguous, while sequences reveal intent.
Detection: A Concrete Scenario
Consider a phishing email that delivers a malicious Word document. The user opens the document, which contains a macro. The macro launches PowerShell with an encoded command that downloads a second-stage payload from a remote server, injects it into a legitimate Windows process (such as svchost.exe), and establishes a persistent scheduled task.
An EDR platform records each step: Word.exe spawning PowerShell, PowerShell making an outbound HTTP connection to an unknown domain, a new DLL loading into svchost.exe memory without a corresponding file on disk (a fileless injection indicator), and a new scheduled task being registered in the Windows Task Scheduler registry hive. No single event is conclusive, but the sequence maps to multiple ATT&CK techniques: T1566.001 (Spearphishing Attachment), T1059.001 (PowerShell), T1055 (Process Injection), and T1053.005 (Scheduled Task/Job). The EDR platform correlates these into a single high-confidence alert with full timeline context.
Response
When a detection fires, EDR platforms can take automated or analyst-initiated response actions:
Response capabilities extend beyond individual endpoints. Modern EDR platforms can search across the entire fleet for indicators derived from one incident, perform bulk remediation actions, and deploy protective configurations to prevent similar attacks.
Implementation Considerations
Deploying EDR without defining alert triage workflows and escalation paths produces alert fatigue. Organizations should configure detection sensitivity in tiers, beginning with high-fidelity rules tied to critical assets and expanding coverage incrementally. Agent rollout should be staged to catch compatibility issues before fleet-wide deployment. Exclusion policies require careful management: overly broad exclusions are a common attacker technique, often achieved by abusing legitimate exclusion configurations to hide malicious activity from the agent.
Performance tuning is essential. EDR agents can consume significant CPU and memory resources during periods of high endpoint activity. Proper configuration includes setting collection priorities, adjusting sampling rates for high-volume events, and establishing resource limits that prevent the agent from degrading endpoint performance during peak usage.
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The security impact of EDR is measurable in dwell time reduction. According to the Mandiant M-Trends 2023 report, the global median dwell time (the period between initial compromise and detection) has fallen from over 200 days a decade ago to 16 days, with organizations that have mature EDR deployments detecting intrusions significantly faster, often within hours. Faster detection means attackers have less time to move laterally, escalate privileges, exfiltrate data, or deploy ransomware.
Without EDR, defenders are operating on incomplete information. Log sources from firewalls and SIEMs record network-level events but cannot tell you which process on which endpoint made a given connection, what that process loaded into memory, or whether it was spawned by a legitimate parent or injected by an attacker. This gap is precisely what attackers exploit through living-off-the-land (LOTL) techniques, which use built-in operating system tools like PowerShell, WMI, certutil, and mshta to execute malicious actions that firewalls and signature-based tools cannot distinguish from normal administration.
A Real Consequence: The SolarWinds Intrusion
The 2020 SolarWinds supply chain compromise, attributed to the threat actor UNC2452 (also tracked as Cozy Bear), demonstrated the consequences of inadequate endpoint visibility. The attackers inserted a backdoor into the SolarWinds Orion software update, which was installed by thousands of organizations. Once active, the backdoor used LOTL techniques and blended into legitimate Orion traffic to avoid detection. Many affected organizations lacked EDR coverage on servers running Orion or had coverage but insufficient monitoring of those specific assets. The intrusion persisted for months at numerous victim organizations before detection. Post-incident analysis confirmed that endpoint telemetry, specifically process trees showing Orion spawning unusual child processes, was the key forensic signal that could have shortened the dwell window.
Economic Impact
The business case for EDR extends beyond security metrics to operational efficiency. Organizations with mature EDR deployments report reduced incident response times from days to hours, decreased forensic investigation costs, and improved regulatory compliance documentation. The FBI's 2023 Internet Crime Report found that organizations with comprehensive endpoint visibility recovered from ransomware incidents 73% faster than those relying on traditional security tools.
Common Misconception
A persistent misconception is that deploying an EDR platform is equivalent to having EDR protection. The platform produces data; it does not produce outcomes on its own. Organizations that deploy EDR but staff no one to review alerts, tune detections, or respond to isolations have invested in a recording system without the analyst capacity to act on it. EDR is a force multiplier for a skilled security team, not a replacement for one.
Another misconception involves coverage completeness. EDR agents must be installed on every managed device to provide comprehensive visibility. Partial deployments create blind spots that attackers can exploit, particularly in server environments where EDR deployment is sometimes delayed due to performance concerns or change control processes.
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The Cyber Defense Alliance approaches Endpoint Detection and Response through the Planetary Defense Model (PDM) under the Threat Intelligence and Detection (TID) domain. The governing methodology is Predictive Defense Intelligence (PDI), summarized as: see the threat before it sees you.
Within this framework, EDR is not treated as a passive monitoring tool. It is an active intelligence collection system that feeds CDA's predictive analysis pipeline. Endpoint telemetry from EDR platforms is one of the highest-fidelity data sources available to defenders because it captures attacker behavior at the point of execution, where intent is unambiguous. A process tree showing a document editor spawning a scripting engine that makes an outbound connection to an unregistered domain is not an indicator to be triaged later; it is an in-progress intrusion requiring immediate response.
CDA's TID methodology maps EDR telemetry directly to ATT&CK technique coverage assessments. Rather than asking "do we have an EDR product deployed," the operational question is: "which ATT&CK techniques are covered by our current detection rules, which are not, and what is the adversary's most probable path given gaps in coverage?" This produces a technique coverage heat map that informs both detection engineering priorities and threat hunting calendars.
CDA differentiates its approach in three specific ways. First, detection content is continuously validated against real adversary tradecraft, not just lab samples. Rules are tested by running known attack tooling in isolated environments and confirming that detections fire as expected before they are deployed to production. Second, EDR telemetry is cross-correlated with external threat intelligence at the indicator and technique level, so that a new campaign reported by an intelligence partner immediately triggers a hunt across enrolled endpoint estates for matching behavioral patterns. Third, response playbooks are pre-approved and pre-tested, meaning that when an EDR alert fires on a critical asset, the analyst has clear authority and documented procedures to isolate, collect, and escalate without waiting for approval chains that allow attackers additional time on the network.
This operational model reflects PDI's core principle: defensive advantage is gained by reducing the time between attacker action and defender response, and that reduction requires both technical capability and organizational process running in parallel. EDR provides the technical capability; CDA's methodology provides the organizational process to activate it effectively.
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