Here is Tip #13 for National Cybersecurity Awareness Month: Limit external sharing default settings.

Many cloud-based collaboration programs come with default settings that allow easy internal and external sharing of information. That means inappropriate data sharing could be happening already without leadership or IT knowing about it.

Steps you can take

You can still achieve effective collaboration in the programs while protecting your data.

Ask your IT department or IT support vendor:
Is external file-sharing enabled? If so, what files are currently being shared?
Is external chat-sharing enabled? If so, is it open to all external orgs or just an allowed list?

Try it out for yourself as a test.
Open a file in Teams or another program, click the share button and see what options are available and what the default option is.

Modify the settings to meet your security needs.

If necessary, engage with a third party.
You might find it necessary to engage a third party if you’re having difficulty determining what access various programs are providing to external and internal accounts.