Table of Contents
What is JIT VM Access and how does it protect Azure virtual machines?
Discover how Just-in-Time VM Access in Microsoft Defender for Cloud minimizes attack surface by providing temporary, controlled access to virtual machines. Learn how JIT reduces exposure to brute-force attacks and unauthorized access attempts.
Question
Which security feature in Microsoft Defender for Cloud helps reduce exposure to potential attacks by limiting access to virtual machines?
A. Just-in-Time VM Access
B. Azure DDoS Protection
C. Azure Firewall
D. Azure Security Groups
Answer
A. Just-in-Time VM Access
Explanation
Just-in-Time (JIT) VM Access in Microsoft Defender for Cloud reduces exposure to attacks by allowing temporary, controlled access to virtual machines only when needed. This minimizes the risk of brute-force attacks and unauthorized access. For more information, please refer to the “Microsoft Defender for Cloud – Overview” lecture.
Just-in-Time (JIT) VM Access is a feature within Microsoft Defender for Cloud that significantly reduces the attack surface of virtual machines by controlling when and how management ports are accessible.
How JIT VM Access Works
Default Deny Posture
JIT VM Access operates on the principle of least privilege by keeping management ports (such as RDP port 3389, SSH port 22, and other common remote management ports) closed by default. These ports are typically targeted by automated brute-force attacks and vulnerability scanners. By keeping them closed except when explicitly needed, JIT dramatically reduces the window of opportunity for attackers.
Time-Bound Access Requests
When an authorized user needs to connect to a VM, they request access through the Azure portal, PowerShell, CLI, or API. The request specifies:
- Which VM they need to access
- Which ports they need (RDP, SSH, or custom ports)
- The duration of access (typically limited to a few hours)
- The source IP addresses that should be allowed
Automated NSG Rule Management
Upon approval (which can be automatic based on Azure RBAC permissions or require manual authorization), Defender for Cloud automatically modifies the Network Security Group (NSG) rules associated with the VM to allow traffic from the specified source IP to the requested port. When the time window expires, the NSG rules are automatically reverted to deny access, re-closing the port.
Security Benefits
Reduced Attack Surface
Management ports are only open for brief, justified periods rather than being continuously exposed to the internet. This minimizes the timeframe during which automated attacks can discover and target these ports.
Audit Trail
All access requests and approvals are logged, providing a complete audit trail of who accessed which VM, when, and from where. This supports compliance requirements and security investigations.
Source IP Restriction
JIT enforces access only from specific source IP addresses, preventing access even during the approved time window if the connection originates from an unauthorized location.
Analysis of Incorrect Options
B. Azure DDoS Protection. This service protects against distributed denial-of-service attacks that attempt to overwhelm resources with traffic. It does not manage access to virtual machines or control management port exposure.
C. Azure Firewall. While Azure Firewall controls network traffic and can filter based on rules, it is a separate service that manages traffic flow at the network level. It does not provide the time-bound, request-based access control mechanism specific to VM management ports that JIT offers.
D. Azure Security Groups. Network Security Groups (NSGs) are the underlying mechanism that enforces traffic rules, but they require manual configuration and don’t provide the automated, time-based access control that JIT delivers. JIT uses NSGs as the enforcement layer but adds the request/approval workflow and temporal access management on top.
Microsoft Security Solutions Capabilities certification exam assessment practice question and answer (Q&A) dump including multiple choice questions (MCQ) and objective type questions, with detail explanation and reference available free, helpful to pass the Microsoft Security Solutions Capabilities exam and earn Microsoft Security Solutions Capabilities certificate.