By J.R. @ Vyogen – Business Process & IT Solutions

Microsoft Teams has become the go-to collaboration hub for many organizations. It’s fast, flexible, and tightly integrated with the rest of Microsoft 365. But behind that convenience are several hidden risks — most of which go unnoticed until there’s a data exposure, permission issue, or compliance audit.

These risks don’t come from Teams being insecure. They come from Teams being easy to use without much oversight. The more Teams your organization creates, the more important it is to understand what’s happening behind the scenes and put the right controls in place.

Here are some of the most common risks — and what to do about them.

Guest Access Without Limits

By default, Teams allows external users (guests) to be added to channels and chats. It’s a great feature for working with partners and vendors, but in many cases, these guests retain access long after the project is over.

The risks:

  • Guest users accessing confidential conversations or files

  • No tracking of what guests were added or when

  • Orphaned guest accounts with persistent access

How to reduce exposure:

  • Limit guest access to specific Teams or domains

  • Set expiration policies for guest users

  • Regularly review and remove inactive or unnecessary external accounts

Private Channels That Create Hidden Sites

Private channels are often used to restrict conversations to a subset of team members. What many admins don’t realize is that each private channel creates its own SharePoint site with separate permissions.

The risks:

  • Fragmented permissions that are difficult to track

  • Sensitive data stored in isolated sites

  • Broken compliance policies due to inconsistent oversight

What to do:

  • Use private channels only when absolutely necessary

  • Track all associated SharePoint sites and include them in governance reviews

  • Apply sensitivity labels and DLP policies to private channel content just like any other site

Oversharing Files Without Labels

When users upload files to a Team, those files are stored in SharePoint. If your organization hasn’t configured sensitivity labels or access policies, those files can be shared beyond their intended audience — both inside and outside the company.

The risks:

  • Files containing customer, financial, or HR data shared too broadly

  • No visibility into who downloaded what or when

  • Difficulty enforcing retention or legal hold policies

How to fix it:

  • Implement mandatory sensitivity labeling for uploads

  • Use DLP policies to detect risky content in real time

  • Educate users on what content should or shouldn’t be shared in Teams

Shadow IT Through Third-Party Apps

Teams supports integration with hundreds of third-party apps. While many are useful, not all are secure — and users can install them without fully understanding what data the app can access.

The risks:

  • Data being accessed by unvetted apps

  • Users unintentionally exposing company content through connected services

  • Lack of logging or control over app behavior

Best practice:

  • Review and restrict third-party app permissions through Teams admin center

  • Approve only apps that meet your security and compliance standards

  • Audit app usage and disable unused or high-risk integrations

Inconsistent Ownership and Lifecycle Management

Teams are often created quickly for a project or initiative — but not always decommissioned when that work ends. Without lifecycle policies, old Teams continue to exist, accumulate data, and remain searchable.

The risks:

  • Sensitive content left in inactive Teams

  • Confusion over which Team is current

  • Increased attack surface due to forgotten access

How to handle it:

  • Assign clear ownership to every Team

  • Use expiration and archiving policies to manage unused Teams

  • Include Team reviews in quarterly governance or compliance processes

Final Thoughts

Microsoft Teams is a powerful collaboration tool, but like any platform, it needs guardrails. Security in Teams isn’t about locking it down — it’s about knowing how it works, what’s being shared, and who has access.

The goal isn’t to limit collaboration. It’s to enable it safely, with confidence that your users can move fast without exposing the business to unnecessary risk.