I have XDR why do I need Sentinel?

This is a question that comes up a lot with security leaders who see Microsoft XDR getting stronger every year.

Microsoft XDR is necessary but not sufficient for many organizations. Microsoft Sentinel exists to solve problems that XDR intentionally does not

Microsoft XDR: What it’s optimized for

Microsoft XDR (Defender XDR) is purpose-built for threat detection and response across Microsoft’s security stack:

Core strengths

Native signals from:
- Defender for Endpoint
- Defender for Identity
- Defender for Office 365
- Defender for Cloud Apps
High-fidelity detections
Automatic attack correlation (incidents)
Built-in response actions (isolate device, reset password, block user)
Low operational overhead

What XDR answers extremely well

“Is there an active attack happening right now across our Microsoft estate?”

XDR is excellent for:

Endpoint, identity, email, SaaS attacks
Reducing alert noise
Fast containment

Design assumption

Data mostly comes from Microsoft-controlled security products
Focused on active threats, not long-term analytics

Sentinel: What it adds beyond XDR

Microsoft Sentinel is a SIEM + SOAR platform, not a replacement for XDR.

It answers a different class of questions.

Visibility beyond Microsoft

Sentinel ingests and correlates data from:

Firewalls (Palo Alto, Fortinet, Cisco)
Network devices
IAM outside Entra ID
VPNs
AWS, GCP
Custom apps and logs
OT / IoT / industry systems

XDR sees attacks inside Microsoft. Sentinel sees the entire enterprise.

Advanced hunting & custom detections

Sentinel enables:

Cross-domain KQL queries (identity + firewall + app + cloud)
Custom analytics rules
Behavioral baselining
Detection of slow, low-and-stealthy attacks

XDR detections are curated. Sentinel detections are customizable.

SOAR and process automation

Sentinel playbooks (Logic Apps) enable:

Multi-system response
Ticketing system integration
Approval workflows
Evidence enrichment
Incident orchestration across tools

XDR response is fast. Sentinel response is process-driven and auditable.

If XDR is “enough,” why do customers still deploy Sentinel?

Because “enough” depends on risk profile.

XDR alone is often enough when:

Mostly Microsoft-centric environment
Small security team
Minimal compliance obligations
Focus on real-time protection

Sentinel becomes necessary when:

Multiple vendors and clouds are in play
Regulatory or audit requirements exist
SOC maturity increases
Leadership asks:

“Can you prove we didn’t miss anything?”

How Microsoft actually intends them to work

This is the key positioning:

XDR = Detection & Response Engine
Sentinel = Security Data Platform & SOC Backbone

Microsoft intentionally:

Pushes high-quality incidents into XDR
Feeds those incidents into Sentinel
Avoids turning XDR into a full SIEM

Why?

Keeps XDR simple and fast
Keeps Sentinel flexible and scalable

Executive-level one-liner (very useful in the field)

XDR tells you you’re under attack. Sentinel tells you how it happened, where else it happened, and how to prove you handled it correctly.

Or even shorter:

XDR protects. Sentinel explains and orchestrates.

Is your team looking to implement XDR or Sentinel or both, our Cybersecurity architect at the Training Boss can help you get it done!.