8 Microsoft Teams Security Tips for Your Business

In short

Overview

The threat has changed too. In 2026, security researchers documented attacks where criminals messaged staff through Teams from outside accounts, then talked them into sharing screens or login details. No software was hacked. The chat window was the way in.

Why it matters

Why Microsoft Teams Security Deserves Attention

Microsoft Teams security matters because Teams touches almost everything sensitive in your business, from client emails and contracts to financial records stored in the background in SharePoint and OneDrive.

Teams encrypts data in transit and at rest and supports strong controls, but the default settings are built for easy collaboration, not tight protection. The gaps are usually in how it is configured, not the platform itself.

Teams comes bundled with Microsoft 365, so its security overlaps with your wider email, file, and identity setup. If you are still weighing your options at a platform level, it helps to understand how Microsoft 365 compares to Google Workspace before locking in your long-term stack.

The 8 tips

Tip 1: Turn On Multi-Factor Authentication for Every Account

Multi-factor authentication (MFA) is the single most effective Teams security setting you can switch on. It asks for a second proof of identity, usually a tap on your phone, on top of the password.

According to Microsoft, MFA blocks more than 99% of account compromise attacks, even when the attacker already has the correct password in hand.

Set it up in the Microsoft 365 admin centre and apply it to everyone, including directors and IT admins, who are the most valuable targets. A few pointers that make it stick:

• Use an authenticator app rather than SMS codes, which can be intercepted.
• Turn on MFA for admin accounts first, then roll it out to all staff.
• Block older sign-in methods (legacy authentication) that skip MFA entirely.

Tip 2: Lock Down External and Guest Access

External and guest access is where most Teams attacks now begin. Out of the box, people from other organisations can often message your staff and request chats without an invite.

Tightening these settings in the Teams admin centre controls who can reach your team from the outside, which shuts down the most common social engineering route.

This is exactly the door the 2026 chat-based attacks walked through. To close it:

• Limit external access to a list of trusted partner domains instead of allowing everyone.
• Turn off open external chat if your business does not need it.
• Review your guest list and remove people whose projects have ended.
• Remind staff that no genuine support team will ask for passwords over Teams chat.

Tip 3: Control Which Apps Staff Can Add to Teams

Every third-party app added to Teams can request access to your files, chats, and calendar. Controlling app permissions stops staff installing tools that quietly pull company data or open a security gap.

Admins can set app permission policies so only approved apps appear across the business, rather than leaving the door open to anything on the store.

Start by reviewing what is already installed, then move to an allow-list approach. Block apps from unknown publishers, and set up a simple approval step so a manager or your IT contact signs off before anything new goes live. It takes a few minutes and removes a lot of hidden risk.

Tip 4: Secure Meetings With Lobby and Presenter Settings

Meeting settings decide who can join, who can share their screen, and who can admit others. Weak defaults let uninvited people slip into calls or take over a presentation. Setting a lobby, limiting who can present, and controlling recordings keeps sensitive discussions private and stops surprises mid-call.

For meetings that involve clients, finance, or personal data, apply these settings as standard:

• Send external guests to the lobby so an organiser lets them in.
• Set presenter rights to organisers only unless someone specifically needs to share.
• Control who can record and transcribe, and tell attendees when a call is being recorded.
• Avoid posting meeting links on public pages or shared inboxes.

Tip 5: Stop Sensitive Files Leaking With DLP and Labels

Data loss prevention (DLP) and sensitivity labels stop confidential information leaving your business by accident. DLP scans messages and files for things like card numbers or PPS numbers and blocks or warns before they are shared.

You configure both through Microsoft Purview. Set policies for the data you actually handle, whether that is client financials, medical records, or staff details. This also supports your obligations under GDPR, and the Data Protection Commission publishes clear guidance for organisations handling personal data that is worth reading alongside your setup.

Tip 6: Back Up Your Teams Data Separately

Microsoft does not fully back up your Teams data for you. Under its shared responsibility model, Microsoft keeps the service running and secure. However, recovering deleted chats, files, and channels is down to you.

Retention settings are not the same as a backup. Retention holds data for compliance, but it will not restore a full channel the way a proper backup can.

Here is roughly where the line sits:

If setting this up feels like one job too many, this is a natural thing to hand to a managed IT support provider who can run and monitor it for you.

Tip 7: Review Who Has Access on a Regular Basis

Access tends to pile up over time. People change roles, projects finish, and guests linger long after they are needed.

Put a short review in the diary every quarter and work through it methodically:

• Remove former staff and any guests who no longer need to be there.
• Use private channels for sensitive work so only the right people see it.
• Give people the minimum access they need to do their job, nothing more.
• Check the audit logs in Purview for unusual sign-ins or sharing activity.

Tip 8: Train Staff to Spot Scams Inside Teams

Staff are the last line of defence in Teams security. Most successful attacks rely on tricking a person, not breaking the technology. Short, regular training helps staff spot fake messages, dodgy links, and screen-share requests from strangers, so they pause before they click or share anything.

Microsoft also offers built-in protections like link scanning through Defender for Office 365, and its own advice on safer messaging in Teams is a good starting point for staff guidance.

Staying secure

Stay On Top of Teams Security

Securing Teams is not a one-off task. It is a set of sensible settings plus a few habits your team keeps up, reviewed every few months as people and projects change. Get MFA, external access, and backups right first, since those three cover the biggest risks, then work through the rest at your own pace.