What is Threat Detection and Response (TDR)? The Complete Guide

How Threat Detection Works

Threat detection is the process of identifying attacker activity within an organization's systems before that activity causes material damage. It is the security capability that converts security investment from passive protection into active defense — the difference between controls that block known attacks and controls that identify novel attacks in progress.

Modern threat detection operates across three data domains that together provide comprehensive visibility into attacker activity. Endpoint telemetry from EDR platforms captures every process, file, network connection, and registry modification on managed devices. Identity and authentication logs from Microsoft Entra ID, Okta, and Active Directory capture every authentication event, access request, and permission change. Network traffic analysis captures connection patterns, protocols, and data volumes that reveal command-and-control communications, lateral movement, and data exfiltration.

The correlation of signals across these three domains — in a SIEM or extended detection platform — is where meaningful threat detection occurs. An anomalous authentication from an unfamiliar location is suspicious in the identity logs. LSASS memory access by an unexpected process is suspicious in the endpoint logs. A large volume of outbound data transfer to an unfamiliar destination is suspicious in the network logs. Each individually might be a false positive. All three correlated to the same user account and timeframe is an incident.

Detection Approaches: Signature, Behavioral, and Anomaly

Threat detection systems apply three detection approaches with different strengths and limitations. Signature-based detection matches observed activity against known patterns of malicious behavior — file hashes, network traffic signatures, command strings associated with known malware. It is highly precise for known threats and generates low false positive rates, but it provides no protection against novel attacks or sophisticated actors who specifically design their tools to evade known signatures.

Behavioral detection identifies activity that deviates from expected behavior patterns, regardless of whether specific tools or techniques have been seen before. A process that normally runs once per day suddenly running 500 times per hour is behaviorally anomalous. A user account that normally authenticates from New York suddenly authenticating from Romania is behaviorally anomalous. Behavioral detection catches novel attacks and living-off-the-land techniques that signature detection misses, at the cost of higher false positive rates that require analyst judgment to triage.

Anomaly detection uses machine learning to establish baselines of normal activity and flag statistical deviations. It provides the broadest coverage but generates the highest false positive rates and requires the most mature data infrastructure and analyst capacity to operationalize effectively.

What Threat Response Actually Involves

Threat response is the sequence of actions taken after a threat is detected to contain the attacker, limit damage, eradicate the attacker's presence, and restore normal operations. It is the operational discipline that converts detection into outcome improvement — a threat detected without effective response is a threat contained only by the attacker's own timeline.

The phases of threat response follow a recognized sequence. Triage determines whether a detected event is a genuine threat or a false positive, and if genuine, its severity and urgency. Containment isolates the affected systems or accounts to prevent the attacker from expanding their access while investigation proceeds — network isolation of compromised endpoints, account suspension for compromised users, blocking of identified attacker infrastructure. Investigation determines the scope of the incident: how the attacker gained access, what they did, what systems they touched, what data they accessed, and what persistence mechanisms they established. Eradication removes the attacker's presence completely — eliminating malware, removing persistence mechanisms, resetting compromised credentials, and patching the vulnerabilities or misconfigurations that enabled initial access. Recovery restores affected systems to normal operation. And post-incident review captures lessons learned and implements improvements to prevent recurrence.

Mean Time to Detect and Mean Time to Respond

MTTD — mean time to detect — and MTTR — mean time to respond — are the operational metrics that determine breach cost. IBM's Cost of a Data Breach research consistently demonstrates that organizations with MTTD under 30 days experience significantly lower breach costs than those with longer detection timelines. Every day of attacker dwell time is additional data exfiltrated, additional systems compromised, and additional persistence mechanisms established that complicate eradication. The MTTD and MTTR targets that translate into meaningful cost reduction — detection within hours for high-severity events, response within minutes for ransomware staging indicators — require continuous monitoring with defined escalation procedures and response authority.

Threat Detection and Response for Mid-Market Organizations

The fundamental question for mid-market organizations is not which detection technology to deploy — it is how to operationalize detection with the analyst capacity and expertise available. Detection technologies are commoditized. The capability that differentiates organizations that contain incidents from those that experience catastrophic breaches is the human operation of those technologies.

For most mid-market organizations between 50 and 500 employees, building internal 24/7 threat detection and response capability is not economically rational. The technology, staffing, and expertise required to operate a genuine SOC — continuous monitoring, threat hunting, incident response — at the scale needed to address 2026 threat actor techniques represents an investment that cannot be amortized over a small number of users. MDR providers deliver this capability as a shared service, providing analyst coverage, detection engineering, and incident response at a per-organization cost that reflects the economics of the shared model.

For PE operating partners, the threat detection and response question is operational rather than technological: who responds when CrowdStrike generates a high-severity alert at 3 AM on a Sunday? If the answer is unclear, the organization's detection capability is contingent on attackers choosing to act during business hours — which they do not. The answer to the 3 AM question determines whether detection capability translates into breach containment.