Secure Guest Access in Microsoft 365 - A simple, straight‑talking guide for small businesses
If you run a small business, chances are Microsoft 365 is at the heart of how your team works.
You probably use:
- Teams to chat and run projects
- Teams channels to keep conversations and files organised
- OneDrive to share files
- SharePoint to store company documents
You might also share files with people outside your business — accountants, subcontractors, consultants, suppliers, or clients.
That collaboration is exactly what Microsoft 365 is designed for.
The risk isn’t using these tools. The risk is how sharing is set up.
The common problem: sharing is easy… and access never goes away
Most small businesses leave Microsoft 365 on its default settings.
Those defaults are built for speed and convenience, which often means:
- links can be shared with “anyone”
- links can be forwarded
- access never expires
- external users don’t need extra security checks
Over time, this quietly creates problems:
- ex‑suppliers still have access
- nobody’s quite sure who can see what
- sensitive files are shared more widely than intended
This usually isn’t careless — it’s just how modern tools behave if no one puts guardrails in place.
A very real scenario
You share a folder with a trusted supplier.
Months later:
- they stop working with you
- their email account is compromised
- someone uses that old access to view or download your files
No hacking. No ransomware. Just trusted access that was never switched off.
What good looks like (in plain English)
You don’t need to lock everything down. You just need a few sensible rules.
1 - Share with specific people, not “anyone”
Files should be shared with named email addresses, not open links. That way:
- people must prove who they are
- access can’t be casually forwarded
- you can see exactly who has access
This one change alone prevents a huge number of accidental data leaks.
2 - Make external access expire
Most external access is temporary.
Good practice is:
- access expires automatically
- it can be renewed if still needed
- old access doesn’t build up in the background
Think of it like visitor passes, not permanent keys.
3 - Add an extra security check for guests
External users should be asked for an extra proof — usually a code on their phone.
If a supplier’s password is compromised, that extra step can stop someone walking straight into your data.
4 - Don’t let guests roam around
External users don’t need to see:
- your staff list
- internal teams
- company structure
They should only see what they’ve been invited to — nothing more.
5 - Be careful with downloads to personal devices
A big risk is files being downloaded to personal laptops or home PCs.
A sensible approach:
- guests can view files in a browser
- downloads are limited where appropriate
- sensitive data stays under control
6 - Protect your most sensitive information
Not all files are equal.
Financial data, customer information, and IP should have extra protection so they can’t be shared externally by mistake — even by well‑meaning staff.
7 - Regularly tidy up old access
The riskiest accounts are often the ones nobody remembers.
A simple quarterly check to remove old guest access goes a long way to reducing risk.
The takeaway
You don’t need to stop collaborating.
You just need to collaborate safely .
Most data breaches today don’t come from dramatic hacks — they come from trusted access that quietly drifted out of control.
With a few sensible Microsoft 365 settings, you can keep sharing easy while massively reducing risk.
Want to find out more?
If you’d like to understand how this applies to your Microsoft 365 setup, or want a quick review of your current sharing settings, feel free to Get in touch .
A short conversation can often highlight simple changes that make a big difference.