Which Azure feature provides Just-In-Time (JIT) VM access to reduce the attack surface of management ports?
JIT VM Access in Microsoft Defender for Cloud is a network-security feature that creates time-limited rules in an NSG (and optionally Azure Firewall) to permit inbound traffic to a VM's management port — commonly 3389 for RDP or 22 for SSH — only from the requesting user's IP address. When the approved session ends or the configured duration expires, Defender for Cloud automatically reverts the rules, removing the port exposure. This shrinks the VM attack surface by ensuring management ports are closed at all other times and aligns with the principle of least-privilege network access.
Why this answer
Just-In-Time (JIT) VM access in Microsoft Defender for Cloud reduces the attack surface by locking down inbound traffic to VMs, only opening management ports (e.g., RDP port 3389 or SSH port 22) when requested and for a specific time window. This is the correct feature because it directly implements JIT access to management ports, as described in the question.
Exam trap
The trap here is confusing Azure Bastion (which provides persistent secure access) with JIT VM Access (which dynamically opens and closes ports on demand), as both relate to securing VM management but solve different problems.
How to eliminate wrong answers
Option A is wrong because Azure Bastion provides secure, seamless RDP/SSH connectivity to VMs over TLS without exposing public IP addresses, but it does not implement Just-In-Time access or dynamically open/close ports. Option C is wrong because Azure AD Privileged Identity Management (PIM) manages just-in-time privileged role assignments for Azure AD and Azure resources, not VM-level network port access. Option D is wrong because Azure Key Vault Certificate access manages certificate lifecycle and secrets, not network-level access control to VM management ports.