Top Microsoft 365 Security Concerns & How To Overcome Them

With over 250 million monthly users, Microsoft 365 is one of the most widely used cloud suites. But this immense popularity and the valuable data stored within the page’s environments pose as appealing targets for cybercrime. In 2022, one in five organizations experienced at least one account compromise in Microsoft 365.

As Microsoft 365 domains continue to be targeted, you must be aware of common Microsoft 365 security concerns and measures you can take to protect your organization. This article will discuss the key Microsoft 365 security challenges, the three layers of their security strategy, and how to keep your company safe from damaging, costly attacks in Microsoft 365. 

What Are the Top Microsoft 365 Email Security Concerns?

To protect your organization against the ongoing threat of cyberattacks on Microsoft 365 environments, you have to be well-informed about common security risks. Below are five frequently occurring Microsoft 365 security concerns you should know.

Privilege Escalation Resulting in Further Malicious Activities 

Privilege escalation is an attack where a malicious actor gains privileges on a system or application they shouldn't have access to. To prevent privilege escalation:

  • Implement role-based access control to restrict access to sensitive systems and applications.
  • Regularly update and patch systems to mitigate known vulnerabilities that attackers can exploit.
  • Use multi-factor authentication (MFA) to protect privileged accounts from unauthorized access.
  • Monitor and log all privileged access attempts to detect suspicious activities.

Bypassing Multi-factor Authentication Leading to Unauthorized Access 

Multi-factor authentication (MFA) is an effective security measure to prevent unauthorized access, but can sometimes fall short, as attackers can still bypass this verification. To prevent bypassing MFA:

  • Use advanced MFA techniques such as biometrics, behavioral analytics, and geolocation-based authentication.
  • Limit the number of authentication attempts to prevent brute force attacks.
  • Use an out-of-band channel for MFA, such as SMS or email, to prevent SIM swapping attacks.
  • Educate employees about the risks of all phishing attack types and to never share MFA credentials with anyone.

Phishing Attacks Putting Sensitive Data at Risk

Phishing attacks are among the most common methods attackers use to steal sensitive information. A recent report states that roughly 20% of all phishing emails had originally been marked as clean or safe to access by the Microsoft 365 Exchange Online Protection (EOP) thus reaching users' inboxes. To prevent phishing attacks:

  • Educate employees about identifying phishing emails and avoiding clicking on suspicious links or attachments.
  • Implement email security measures such as spam filtering, anti-phishing, and malware protection software.
  • Use web filtering to block access to known malicious websites.
  • Conduct regular phishing simulations through sandboxing malware to train employees effectively to respond to cybersecurity phishing attacks.

Malicious Macros Threatening Critical Systems 

Malicious macros are malware that uses macros embedded in documents to execute malicious code. To prevent malicious macros:

  • Disable macros in documents by default and only enable them on a case-by-case basis.
  • Implement file blocking to prevent the execution of files that contain malicious macros.
  • Use malware protection software to detect and remove malicious macros.
  • Educate employees on the risks of opening suspicious documents and how to report them to IT.

Data Exfiltration Leading to the Compromise of Sensitive Information

Data exfiltration is the unauthorized data transfer from a system or network to an external location. To prevent data exfiltration:

  • Implement data loss prevention (DLP) solutions to monitor and block unauthorized data transfers.
  • Implement Microsoft email encryption services to protect sensitive data from being accessed by unauthorized users.
  • Use firewalls and intrusion detection/prevention systems (IDS/IPS) to detect and block suspicious network traffic.
  • Educate employees about the importance of data security and data exfiltration risks.

Why Do Threat Actors Target Microsoft 365?

Cybercriminals use increasingly complex and sophisticated tools to target Microsoft 365 environments to steal sensitive information. They even use Microsoft capabilities, such as Static Web Apps, to create false landing pages containing the Single Sign-On (SSO) option to harvest Outlook, Office 365, and other credentials. Attack vectors can be found in Microsoft Office Online, Outlook, OneDrive, Sharepoint, Microsoft Teams, and third-party cloud providers. 

Clients are responsible for their network security under shared protection models. The threat level has increased as malware ransomware and phishing attacks have become cheaper and easier to facilitate, with ransomware kits being sold on the dark web. Attackers target Microsoft 365 for several reasons, including:

Why Threat Actors Target Microsoft 365 Guardian DigitalDownload

  • High profitability: Depending on the target, attacking Microsoft 365 can be highly lucrative for cybercriminals, as sensitive data and information stored within the platform can be valuable on the black market.
  • Widespread use: More and more businesses are migrating their essential data and functions to Microsoft 365, making it a prime target. Its integration and ease of use have reduced friction, and streamlined services and communication, making it an attractive option for organizations.
  • Third-party cloud applications: Using third-party cloud applications within Microsoft 365 provides additional attack angles that may be difficult to spot and secure, increasing the risk of a successful attack.
  • Lack of multi-factor authentication: Certain users may have yet to embrace MFA, making it easier for attackers to gain unauthorized access. Users without multi-factor authentication are attacked 10 times more often than those who use it, making it a significant risk factor.
  • Machine learning: Attackers now use machine learning algorithms to download data en masse and sift through it as they maintain their compromised account access. This allows attackers to steal large amounts of data more efficiently and potentially remain undetected for longer periods.

Microsoft 365 Vulnerabilities

Microsoft 365 is a popular productivity suite used by many organizations worldwide. While Microsoft provides several security mechanisms to protect Microsoft 365 assets from malicious software, it's still important to be aware of vulnerabilities that could lead to security breaches.

Recently, Microsoft has significantly invested in improving its threat and vulnerability management experiences in Microsoft 365. As part of this effort, they have combined existing product experiences and functionalities to enhance security capabilities that protect, detect, investigate, and respond to email, collaboration, identity, and endpoint threats.

Despite these efforts, vulnerabilities can still exist in Microsoft 365 security. For instance, in 2021, researchers found a vulnerability in Microsoft Teams that could have allowed hackers to access sensitive data, including conversations and files, from Teams accounts. The exposure had been present for over a year before Microsoft discovered and patched it.

Another example of a vulnerability in Microsoft 365 that was exploited for over a year is the "ZeroLogon" vulnerability, discovered in August 2020, which allowed attackers to gain control of a domain controller and ultimately take over an entire network. Microsoft released a patch for the vulnerability in August 2020, but many organizations needed to be faster to apply the patch, leading to several successful attacks.

To protect against these and other vulnerabilities, organizations should stay current on the latest security patches and ensure that they are promptly applied to all Microsoft 365 assets.

What Are The Three Layers of Microsoft 365 Email Security?

Microsoft's security strategy is based on a three-layer approach: prevention, detection, and response to cyber threats.


Microsoft implements various measures to prevent attacks, such as encryption, access controls, and regular security updates to its products. They also leverage Machine Learning and Artificial Intelligence to identify and block threats in real-time.


Microsoft uses various tools to detect threats, including real-time monitoring, behavioral analytics, and threat intelligence. They also conduct regular security assessments to identify vulnerabilities and improve their security posture.


In the event of email security breaches, Microsoft has a team of experts dedicated to incident response. They follow a well-defined incident response plan, including containing the breach, assessing the damage, and implementing remediation measures.

Both External & Internal Threats Are a Serious Concern for Microsoft 365 Users

Cloud computing information technology concept, data processing and storage platform connected to internet network, specialist engineering systemWhile external threats pose a significant risk, internal threats are also among the top security concerns in Microsoft 365. Unauthorized file sharing and privilege abuse are some of the critical problems that can occur. Although the platform has features to safeguard data from unauthorized access, granting permissions too easily can result in serious issues.

Sharing files with others requires trust that they will handle the data appropriately. Even if the sender takes all necessary precautions, an irresponsible recipient leaving their account open on a public device can risk the sender's account.

To mitigate these risks, limiting access to files and ensuring recipients understand the importance of Internet safety is crucial. Organizations should establish strict access controls and provide regular Microsoft 365 security training to their employees to avoid the risks of internal security breaches.

Top Microsoft 365 & Cloud Email Protection Tips 

The Microsoft Secure Score

Microsoft Secure Score is a measurement of an organization's security posture, with a higher number indicating more recommended actions taken, and provides a list of recommended steps that you can take to improve the security of your organization. It has recently been updated to support security defaults in Azure Active Directory, making it easier to help protect your organization with pre-configured security settings for common attacks.

Enable Multi-Factor Authentication

Multi-factor authentication (MFA) adds an extra layer of security to your organization by requiring users to provide additional authentication factors beyond their passwords to access their accounts. Enabling MFA for all users and login methods with Azure AD Security Defaults is recommended. This option allows you to easily and quickly enforce MFA for all users in your environment with a stringent policy to challenge administrative accounts and administrative logon mechanisms.

Discover and Classify Critical Assets

Knowing what your critical assets are is essential in protecting them. Microsoft recommends discovering and classifying your critical assets. Once you've identified them, you can prioritize protecting them from threats.

Enforce Least Privilege Access

Enforcing "least privilege" access means giving users only the access they need to perform their jobs and nothing more. This helps reduce the risk of a data breach or other email security incident. Microsoft recommends enforcing "least privilege" access.

Enable Unified Audit Logging

Unified Audit Logging provides a centralized view of your environment's user and administrator activity. It helps you detect and investigate potential security incidents. Microsoft recommends enabling Unified Audit Logging.

U.S. Government Agencies Impersonated in Microsoft 365 Phishing Attacks

A persistent phishing campaign aimed at U.S. government contractors has expanded its tactics to employ higher-quality lures and more sophisticated documents. The campaign uses phishing emails that entice recipients with requests for bids on lucrative government projects, redirecting them to phishing pages designed to appear as legitimate federal agency portals.

m365 headline

Initially targeting the U.S. Department of Labor, the threat actors have expanded their focus to include the Department of Transportation and the Department of Commerce. The campaign has undergone careful revisions, including consistent formatting and more prominent logos in phishing emails, simplified and smaller PDF files with these logos and department-specific metadata, improved phishing web page behavior with HTTPS encryption, and a Captcha Challenge step on the phishing page.

The threat actors have also adopted long domain names to appear legitimate, particularly on mobile browsers. With the campaign continuously evolving and closely mimicking genuine bid requests and state bidding portals, it becomes challenging to detect signs of fraud. To defend against these attacks, recipients should scrutinize details such as the sending address and landing URL and consider accessing bidding portals through search engines rather than provided links.

Keep Learning About Microsoft 365 Vulnerabilities & How To Overcome Them

Many have decided that the advantages of Microsoft 365 outweigh the risks. Organizations must take a comprehensive approach to mitigate critical vulnerabilities in their Microsoft 365 environment. Consistent evaluation and maintenance are necessary to achieve a strong security posture. Critical additional security defenses provided via a cloud-based email security software solution are also essential in fortifying Microsoft 365 security against attacks leading to compromised email addresses. Organizations can better protect their Microsoft 365 environment from potential security threats by implementing the strategies and tools shared in this article.

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