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defender-for-servers

Security & auditing

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Updated 10-16 02:29

About this skill

Microsoft Defender for Servers

Defender for Servers is the server-focused plan inside Microsoft Defender for Cloud. It extends Microsoft Defender for Endpoint (MDE) to Azure VMs, Azure Arc-enabled machines (on-prem, AWS EC2, GCP Compute), and VM Scale Sets, and adds server-specific controls: just-in-time VM access, file integrity monitoring, agentless disk scanning, and vulnerability assessment.

When to use

Designing or hardening protection for server workloads — IaaS VMs, hybrid/multicloud servers via Arc, jump hosts, domain controllers, line-of-business servers. Use this skill for plan selection, MDE-for-Servers onboarding, FIM, JIT, and agentless vs agent-based scanning trade-offs.

Do not use this skill for client endpoints (defender-for-endpoint), AKS/container hosts (defender-for-containers), Azure storage accounts (defender-for-storage), or generic Defender for Cloud posture (defender-for-cloud-hardening).

Pick the plan

If you need... Plan
Free foundational CSPM only (no server EDR) Defender CSPM (no server plan)
MDE Plan 2 EDR, threat detection, free 500 MB/day Log Analytics ingestion Defender for Servers Plan 1 (per-server)
Everything in P1 plus FIM, JIT, agentless scanning, vuln assessment, adaptive app controls, network hardening, regulatory compliance, 500 MB free ingestion Defender for Servers Plan 2

Rule of thumb: Plan 1 = "I just need EDR everywhere." Plan 2 = "I need EDR + posture + compliance + FIM." Most enterprises pick P2 for production, P1 for dev/test.

Onboarding paths

Estate Path
Azure VMs Enable plan at subscription scope; auto-provisioning deploys MDE + Azure Monitor Agent
On-prem / VMware servers Azure Arc onboarding, then enable plan
AWS EC2 / GCP Compute Connect AWS account / GCP project to Defender for Cloud; auto-provisioning via Arc
VMSS (uniform) Plan applies; agentless scan covers ephemeral instances

Approach

  1. Inventory and connect first. Onboard non-Azure servers via Arc before enabling the plan; otherwise you pay per-server but get no coverage on hybrid estate. Verify: Defender for Cloud → Inventory shows all expected resources with a Defender plan column = Plan 1/2.

  2. Enable Plan 2 at subscription scope (not resource group) so new VMs inherit automatically. Use Azure Policy Configure Microsoft Defender for Servers to be enabled at the management group for multi-sub estates.

  3. Turn on auto-provisioning of MDE integration. This pushes the MDE sensor via the unified solution; do not also onboard servers directly through Intune or local script — it causes telemetry duplication and double billing. Verify: a sample VM appears in security.microsoft.com → Device inventory within 1 hour.

  4. Enable agentless disk scanning. Reads VM disk snapshots to find malware, secrets, and vulnerabilities without any agent — runs once per 24h, no performance impact. Verify: Recommendations → "Machines should have a vulnerability assessment solution" green for VMs without MDE Vulnerability Management agent.

  5. Configure JIT VM access for any VM with management ports (RDP 3389, SSH 22, WinRM 5985/5986). Default to 3-hour max request, source IP = requestor only. Verify: NSGs show JIT-managed deny rules for the protected ports; access requests show in activity log.

  6. File Integrity Monitoring via MDE (the Log Analytics-based FIM is being retired). Enable on tier-0 servers (DCs, PKI, jump hosts) first. Tune the rule set — default includes Windows system files; add your app's config paths. Verify: FIM events appear in MDE advanced hunting DeviceFileEvents with ActionType = FileCreated/Modified on the monitored paths.

  7. Adaptive application controls (Plan 2). Run in audit for 14 days to learn the app baseline per VM group, then enforce. Skip on highly dynamic workloads (CI build agents).

  8. Free 500 MB/day Log Analytics ingestion. Stream the security event set to a workspace you can query from Sentinel — but keep the volume budget in mind; high-volume DCs blow past 500 MB easily.

  9. Review the regulatory compliance dashboard (PCI, ISO 27001, NIST 800-53, CIS) monthly and turn failed controls into Azure Policy assignments.

Guardrails

  • Onboard hybrid via Arc, not local MDE script. Direct MDE onboarding bypasses Defender for Cloud billing/posture and you lose JIT, FIM, agentless scan.
  • Do not enable both Plan 1 and Plan 2 in the same scope. P2 supersedes P1; configure at the highest scope and let inheritance work.
  • JIT changes NSG rules, not Azure Firewall / NVA rules. If management traffic flows through a firewall, JIT alone won't protect — add firewall policy.
  • Agentless scan is point-in-time. It catches drift every 24h, not real-time. Keep MDE on for runtime detection.
  • FIM via MDE is the supported path. The legacy Log Analytics-agent FIM is deprecated — do not architect new deployments around it.
  • Do not run two AV engines active. If a third-party AV is primary, set Defender to passive + EDR in block mode (see defender-for-endpoint).

Common anti-patterns

  • "We turned on Plan 1 everywhere to save money" then asked for FIM/JIT — those are P2 features. Move prod to P2.
  • "MDE onboarded directly through GPO on Arc servers" — bypasses DfC, loses billing integration, double-onboarded. Always via DfC auto-provisioning.
  • "JIT request window = 24 hours, any source IP" — defeats the point. Cap at 3h, source IP locked.
  • "FIM enabled on every file path on every server" — alert fatigue. Tier-0 systems + app-specific config paths only.
  • "Adaptive application controls enforce on day one" — blocks legitimate admin tooling. 14 days audit, then enforce.
  • "Skipped agentless scan because we already run MDE Vulnerability Management" — they're complementary; agentless catches unmanaged disks and stopped VMs.

Example prompts

  • Plan Defender for Servers P1 vs P2 for a 2,000-VM estate split 70/30 prod/dev.
  • Onboard 500 on-prem Windows Servers via Arc and enable P2.
  • Roll out JIT VM access to all production Linux jump hosts with a 2-hour max window.
  • Configure FIM via MDE on tier-0 domain controllers — which paths and registry keys?
  • Stream Defender for Servers events into Sentinel using the 500 MB free allowance — what do we ingest?
  • Connect an AWS account with 300 EC2 instances and enable Defender for Servers P2.
  • Tune adaptive application controls for a fleet of IIS web servers.

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