Teams Access Tokens: A Storm in a Teacup?
Recently, there’s been some chatter online about a supposed new method for stealing Microsoft Teams access tokens. As a Managed Service Provider, we understand that any news concerning security can cause concern, and we’ve been asked if this is something businesses need to worry about. Our take? Not really, and here’s why.
The core of the issue, as reported, involves accessing a local state file used by the Microsoft Teams client. This file, located within the user’s local application data, contains information necessary for Teams to function. The reports suggest that attackers could extract cookies from this file, which are then used to obtain access tokens. These tokens, in turn, could theoretically be used to interact with Teams via the Graph API.
Now, let’s break down what this actually means for your business.
Firstly, this isn’t entirely new territory. The process of extracting and decrypting cookies from applications that utilise Chromium-based components isn’t a novel concept. Many browsers and applications built on similar frameworks use encrypted data storage for session information. The new Teams client, in fact, relies on the WebView2 component, which uses the Edge rendering engine. This integration means Teams shares some architectural similarities with Chromium-based browsers, including the use of local state files and the Data Protection API (DPAPI) for encrypting sensitive data.
The crucial point here is the pre-requisite for this “attack.” For an attacker to even get to the Teams local state file and the associated cookie database, they would first need to have successfully compromised a user’s workstation. Think about it: if someone has gained full access to a computer, they’ve already bypassed significant security layers. At that point, they could likely open the Teams application directly and send messages without needing to engage in the complex process of extracting and decrypting tokens. The ability to access the workstation in the first place is a far more serious compromise than the ability to send a few Teams messages programmatically.
Furthermore, the claim that these tokens could be used to send emails is also inaccurate. The access tokens obtained from the Teams client are specifically for Teams-related actions. They do not grant permissions to interact with Exchange Online or send emails.
While we commend the work of security researchers in identifying potential vulnerabilities, it’s important to maintain perspective. This particular finding, while technically interesting, doesn’t represent a significant new threat to businesses if their existing security practices are robust.
What Really Matters for Your Security
The most effective defence against sophisticated attacks isn’t necessarily focusing on the minutiae of how specific applications store data. It’s about building a strong foundational security posture.
- Multi-Factor Authentication (MFA): This is your absolute strongest line of defence. By requiring more than just a password to log in, you drastically reduce the risk of account compromise, even if credentials are stolen.
- Endpoint Security: Ensuring your workstations are protected with up-to-date antivirus, endpoint detection and response (EDR) solutions, and regular patching is vital. This directly addresses the scenario of an attacker gaining access to a device.
- User Awareness Training: Educating your staff about phishing attempts and social engineering tactics is paramount. Many successful compromises begin with a user clicking a malicious link or downloading an infected attachment.
At Byte By Byte, we are dedicated to keeping your IT environment secure and running smoothly. While this latest Teams token news might seem alarming, it highlights the importance of focusing on comprehensive security strategies rather than isolated technical exploits.
If you’re concerned about your current security posture or want to ensure you have the right defences in place to protect your business from evolving threats, get in touch with our team today. We can help you navigate the complexities of IT security and implement robust solutions tailored to your needs.