Mitigating the latest Microsoft Teams vulnerability with Netskope

Johannesburg, 02 Aug 2023

A team of experts from JumpSEC Labs discovered a vulnerability in Microsoft Teams that allows malicious actors to bypass policy controls and introduce malware through external communication channels, leaving end-users susceptible to phishing attacks.

Microsoft’s advice is to educate end-users to detect phishing attempts. One workaround would be to disable Microsoft Teams collaboration with external organisations.

This particular vulnerability in Microsoft Teams enables threat actors to bypass existing policy controls, allowing them to share links to malicious files within Teams chats, without the end-user ever accepting a message request. This circumvention of security measures can have severe consequences for organisations, especially considering that Microsoft Teams boasts a user base of 300 million users worldwide.

To make matters worse, this attack does not rely on e-mail, bypassing traditional e-mail security measures and abusing the inherent trust end-users have with collaboration tools. Besides end-users, many organisations inherently trust SaaS as a reliable source as well. This translates to security controls where trusted sources are not inspected and thus bypassed.

The Netskope Threat Labs Stats for June 2023 blog revealed that 60% of all malware downloads through HTTP/HTTPS were traced back to popular cloud apps. Additionally, 32% of SaaS-delivered malware originated from OneDrive and SharePoint, indicating the need for strengthened security measures on these platforms. The notion that SaaS is considered a ”trusted source” directly contradicts the fundamental principle of zero trust.

Based on these principles, organisations should always inspect all downloads for threats, regardless of their origin. This approach allows organisations to enable external parties to share content while still leveraging Netskope Advanced Threat Protection to block malicious file transfers.

To effectively combat such threats, organisations need a comprehensive cyber security solution that follows the principles of zero trust and secure access service edge (SASE). Netskope implements these principles through its private cloud platform regardless of an organisation’s location or the nature of their workloads (Web, SaaS, VPC, IaaS, etc), protecting users and machines across various environments.

The power Netskope provides is the ability to identify and control the usage of specific SaaS instances within a service. This granular control empowers organisations to mitigate and manage risks effectively while enabling collaboration across multiple SaaS platforms. By implementing Netskope, organisations can protect users from interacting with unknown and unmanaged SaaS applications, including those originating from desktop clients like Microsoft Teams. Additionally, Netskope allows organisations to enforce limitations on SaaS activities, such as sharing, liking, reposting and downloading files, especially when they involve trusted external partners.

These capabilities make it possible to protect end-users against these phishing attacks as shown in the diagram below.

Figure 1: MS Teams Abuse.
Figure 1: MS Teams Abuse.

Additionally, to enable these security measures, Netskope leverages advanced threat protection techniques such as sandboxing and data protection. These features allow for the scanning of sensitive information, such as personally identifiable information (PII), source code or medical records, to identify potential threats or policy violations. By combining these advanced measures with the robust Netskope security platform, organisations can effectively defend against emerging threats.

Netskope’s Advanced Analytics capabilities provide security teams with specific dashboards and valuable insights to assess the risk of rogue cloud instances being exploited for malware delivery or the potential of anomalous communications targeting the organisation. Rich details and comprehensive analysis empower security teams to make informed decisions and streamline the mitigation and remediation processes. The Sankey diagram below showcases a visual representation of the interaction between various SaaS, the used instances, and their respective activities.

Figure 2: Netskope Advanced Analytics Dashboard to assess the risk of rogue cloud instances.
Figure 2: Netskope Advanced Analytics Dashboard to assess the risk of rogue cloud instances.

The Microsoft Teams vulnerability discussed in this press release highlights the importance of comprehensive visibility, understanding and control of SaaS, the instances, and the activities within.

By leveraging the comprehensive security solutions offered by Netskope, organisations can effectively protect themselves from emerging threats and vulnerabilities by applying zero trust, advanced threat protection and robust data security measures.

To learn more on how Netskope can help your organisation mitigate similar risks via instance awareness, watch this demo: Defending against cloud threats with instance-awareness. Additionally, to learn more about the latest emergent cloud-native threats, and how Netskope can mitigate them, subscribe to the Cloud Threats Memos so you don’t miss a threat!