It is very easy to check whether your document is shared with someone via guest links. You just need to check the menu “Properties” for this particular document. This guest links can be disables any time you want.
This can be done following these instructions:
1. Start with signing in to your personal account on Office 365.
2. Look at the left corner of your page and press the icon for launching the application.
3. Press the tile “SharePoint” and then “SharePoint” at the very top side of your page.
4. Now, you will need to go to the library which stock your document and where you want to disable the guest link.
5. You will see ellipses and you will need to press “Share”.
6. Now, you can see a dialog box “Share” in front of you where you have to press “Get a link”.
7. Click the option “Remove”.
8. You will be asked if you want to disable this guest link and you must approve clicking “Disable Link”.
9. Finally, press “Close”.
Now, when someone who does not belong to your organization will try to get access to your document using his old guest link, this person will receive a message telling him has access has been disabled.