PUBlished on
February 2, 2024
updated on
November 5, 2025

Behind The Breach: Microsoft Breach by Russian Hackers

FARAH IYER AND GLENN CHISHOLM

On 12 January 2024, Microsoft disclosed a critical breach carried out by Russian state-sponsored group, Midnight Blizzard. The threat actor used a password-spraying attack to gain unauthorized access to Microsoft Corporation’s Office 365 tenant–affecting the accounts of senior leaders and members of Microsoft’s cybersecurity and legal teams.  

Who is Midnight Blizzard?

Midnight Blizzard, also known as Nobelium, APT29, and Cozy Bear, is a well-known threat actor. The group was responsible for the SolarWinds Hack, one of the most significant cybersecurity attacks in history. In that attack, malicious code was inserted into SolarWinds’ Orion software–affecting thousands of organizations (including the US government) and causing billions of dollars in damages.

While the Microsoft breach had a relatively limited impact, the threat actor managed to evade detection for months, reflecting their persistent and stealthy nature. Now, let’s explore the attack timeline in further detail…

Microsoft breach timeline:

Why it Matters

This incident reflects the ongoing threat posed by nation-state actors and the need for proactive measures to secure SaaS applications as they become even more vulnerable to attacks.

Midnight Blizzard’s more recent breach of Hewlett Packard Enterprise (HPE) is yet another example of this. The breach, which began in May 2023, went undetected for several months. During this time, the threat actor gained unauthorized access to HPE’s cloud-based email environment leading to the exfiltration of corporate data.

What Can You Do to Protect Your Organization?

Below, we offer guidance to help you secure your SaaS applications against attacks like the Microsoft breach. We outline measures to reduce the risk of breaches (prevention) and detect and stop threats early in the kill chain (mitigation).

At a Glance

Prevent SaaS compromise by:

Mitigate threats by:

Let’s now explore each of these measures in further detail…

1. Enforce mandatory reviews for privileged accounts

User access reviews are crucial for security and IT teams to enforce the principle of least privilege. This helps minimize data exposure to only what is necessary. In the case of a breach, restricting data access limits the impact of the threat, preventing it from causing further damage to the organization.

Obsidian offers tools to help you do this effectively. Our platform allows you to:

2. Identify and remove inactive privileged accounts

As illustrated in the Microsoft breach, inactive accounts can pose a significant security risk. These accounts serve as an ideal entry point for threat actors to gain unauthorized access, as they often go unmaintained and unnoticed by security teams.

You can use Obsidian to help you efficiently detect these accounts, particularly those with special privileges. Inactive account alerts like the one below, play a crucial role in helping you identify, tune, or deprecate accounts, resulting in a reduced attack surface for threat actors.

3. Leverage controls that block unauthorized integrations

The rise of interconnected SaaS applications poses new challenges for organizations. As integrations become more seamless, the risk of unauthorized or insecure third-party applications increases.

Using Obsidian’s controls, you can block unauthorized applications from accessing your environment (as shown below). Obsidian also provides filters that offer immediately actionable data, surface risky permissions, user activity levels, and specific detections related to suspicious integration activities.

4. Identify and remove high-risk applications

Applications are typically classified as “high risk” if they access sensitive data, have weak authentication, or exhibit other qualities that increase their vulnerability.

Obsidian’s Integration Risk Management (IRM) capabilities help you:

As shown below, our platform promptly identifies high-risk applications. In this instance, it flags those applications that can read all mailbox content, as experienced in the Microsoft breach.

As demonstrated below, you can configure triggers that automate the removal of high-risk applications, tailored to the needs and risk tolerance level of your organization.

If the application was not removed by the team during review, an extra layer of detection can be added, which would classify the application as a threat:

5. Identify and swiftly address user compromise

Addressing user compromise in a timely manner helps minimize additional fallout from a breach. Obsidian provides a range of tools to help you conduct Identity Threat Detection and Response (ITDR).

Obsidian collects data from your SaaS applications, analyzing activity, configurations, and user behavior to understand what normal looks like within your environment. In the event of anomalies, such as impossible travel, Obsidian ensures you receive immediate, accurate and low-noise alerts. These alerts come with actionable insights that seamlessly integrate with your existing workflows for efficient incident response.

Final Thoughts

The recent spate of attacks by Midnight Blizzard is undoubtedly concerning. SaaS applications are increasingly the lifeblood of many organizations. Securing these applications is critical to minimizing and managing business risk for all organizations. As this blog post highlights, there are a number of actions you can take to secure your SaaS applications today.

For more information on how Obsidian can help you, download The Forrester Wave™: SaaS Security Posture Management, Q4 2023, or schedule a demo today.

Frequently Asked Questions (FAQs)

What was the method used by Midnight Blizzard to breach Microsoft's Office 365 accounts?

The Midnight Blizzard group used a password-spraying attack to gain unauthorized access to Microsoft’s Office 365 tenant. This type of attack involves trying a limited number of common passwords against many accounts, taking advantage of weak or reused credentials especially on privileged accounts. This allowed them to compromise accounts belonging to Microsoft’s senior leadership and security teams. ---

Who is Midnight Blizzard and what are they known for?

Midnight Blizzard, also referred to as Nobelium, APT29, or Cozy Bear, is a Russian state-sponsored threat actor. They are notorious for carrying out the SolarWinds hack, which affected thousands of organizations, including several U.S. government agencies, and resulted in billions of dollars in damages. They are known for highly sophisticated, stealthy cyber-espionage campaigns against major enterprises and government targets. ---

Why are inactive privileged accounts considered a major security risk?

Inactive privileged accounts are a common weak point because they often go unnoticed and unmaintained by IT or security teams. Attackers can exploit these accounts to gain elevated access without triggering immediate suspicion, as seen in the Microsoft breach. Regularly identifying and removing or securing these accounts reduces the attack surface and limits opportunities for unauthorized access. ---

What steps can organizations take to prevent breaches similar to the Microsoft incident?

Organizations should enforce mandatory reviews of privileged accounts, promptly identify and remove inactive accounts, and implement controls to block unauthorized third-party integrations. Regular user access reviews and continuous monitoring for suspicious activities, combined with tools like multi-factor authentication, can significantly lower the risk of account compromise. Utilizing platforms like Obsidian can automate these processes and provide actionable alerts for early threat detection. ---

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