Microsoft Defender vs Sentinel: What’s the Difference?

Microsoft’s security portfolio can feel like alphabet soup. Two names that often get mixed up are Microsoft Defender and Microsoft Sentinel. They sound similar, both deal with cyber security, and both sit under the Microsoft security umbrella — but they serve very different roles.

In this blog, we’ll explore what each does, where the overlap lies, and why you might need both.

The confusion starts with the branding. “Defender” has been around for years — many know it as the built-in antivirus on Windows machines. But in Azure and Microsoft 365, Defender now refers to a whole family of Extended Detection and Response (XDR) tools that protect workloads, identities, endpoints, and data.

Microsoft Sentinel, on the other hand, is a much newer service. It’s Microsoft’s cloud-native Security Information and Event Management (SIEM) and Security Orchestration, Automation and Response (SOAR) tool. Instead of directly protecting workloads, it collects, correlates, and analyses security data across your environment.

Put simply:
– Defender fights the fires on the ground.
– Sentinel is the watchtower spotting threats from above.

Microsoft Defender (in Microsoft Azure often called Defender for Cloud) is about protection and response at the workload level. It monitors specific resources — VMs, databases, containers, identities — and flags suspicious activity.

Key points:

• Scope: Protects individual resources such as virtual machines, SQL databases, storage accounts, and even endpoints outside Azure.
• Function: Detects and blocks threats in real time. For example, if a VM starts making suspicious outbound connections, Defender can alert you and even take automated action.
• Integration: Works natively with Azure services, but also extends to hybrid and multi-cloud workloads.
• Use case: An IT team wants to protect a set of servers or a database against malware, brute-force attacks, or misconfigurations.

Think of it as the XDR tool that fights threats directly where they appear.

Microsoft Sentinel is not focused on protecting a single machine or database. Instead, it’s about collecting and making sense of security data across the entire estate.

Key points:

• Scope: A SIEM/SOAR platform for security teams, collecting logs and signals from Azure, on-premises, and third-party tools.
• Function: Correlates events, applies AI/ML to detect patterns, and helps security analysts investigate and respond to incidents.
• Integration: Defender feeds its alerts into Sentinel, alongside data from firewalls, identity platforms, and SaaS apps.
• Use case: A security team wants to understand whether a failed login attempt on a SQL server, unusual traffic from a firewall, and a phishing email are part of the same coordinated attack.

Think of it as the central command centre, giving you visibility and context across the whole environment.

The short answer: it depends on your size, maturity, and security needs.

Smaller businesses with limited resources often find Microsoft Defender alone is enough. For example, a 50-person law firm that’s mostly cloud-based and doesn’t have a dedicated security team can rely on Defender for Cloud. It provides real-time protection for VMs and databases, blocks brute force attempts, and surfaces clear alerts. Adding Microsoft Sentinel here could generate more noise than value, as there may not be staff available to interpret and act on the data.

Organisations operating under regulatory pressure — such as financial services firms — usually need Defender and Sentinel working together. Defender protects workloads directly, while Sentinel pulls in logs from multiple sources, creating an audit trail that supports compliance frameworks like ISO 27001 or FCA standards. This combination helps IT teams demonstrate their security posture to auditors without drowning in manual reporting.

Larger enterprises or high-risk sectors (think healthcare or retail with thousands of users) almost always require both Microsoft Defender and Sentinel. Defender provides frontline detection, while Sentinel stitches together signals from across hybrid environments and SaaS platforms to build attack timelines. This gives security analysts the context they need to investigate quickly and reduce response times.

For organisations in growth mode, a phased approach can be effective. Many start with Defender to establish workload-level protection and then adopt Sentinel later, as security operations mature. This way, they avoid being overwhelmed on day one but still build towards proactive monitoring and incident response.

Microsoft Defender and Microsoft Sentinel are complementary, not interchangeable. Defender provides the immediate detection and protection needed at the workload level, while Sentinel gives organisations the broader visibility and incident management capabilities required to manage modern threats.

For IT professionals exploring Microsoft’s security stack, the key takeaway is: Defender protects, Sentinel oversees.

At Synextra, we help organisations cut through the branding noise and implement the right mix of Microsoft security tools — making sure they work together effectively to protect your business.