Somebody sends you a link to a Google Sheet and it just works. It’s magical.
But that magic comes at a cost. I see far, far too many organizations that regularly share Google Documents and Sheets by using the share with “Anyone with the link” option that Google easily provides.
That is almost ALWAYS a bad idea. The convenience of having it shared with anybody is, at the same time, a potential security problem today and in the future.
But that long link with the 44 random-looking characters would be impossible for somebody to guess, right?
Yes. It would be statistically improbable for somebody to just guess a random string of 44 characters that would result in an actual document. It is possible that an attacker could write programs that could guess millions and millions of links to try them until they found some documents that actually exist. But that’s not the most likely weakness.
Consider what happens when you email a for your spreadsheet to somebody else. You have zero control over who accesses it after that. What if the recipient forwards your email with the link to somebody else? Often emails to businesses are forwarded into Customer Relationship Management (CRM) or similar systems where that link is now accessible to many other people in the organization. What if an attacker has access to a recipients email? Or a CRM system? How about if an employee leaves the company and they still have it in a browser history.
In all of those scenarios, and hundreds more that you can’t imagine, if your document is shared with “Anyone with the link”, literally anybody that sees that link can open it and you have absolutely no knowledge that they did.
Always share only with specific email addresses.
Sharing with Google Groups
Sharing with specific people can become a headache to maintain as people change roles. Consider using the Google Groups feature in your organization. You can set up a Google Group for something like ‘firstname.lastname@example.org’ or ‘email@example.com’ and ask to have documents shared with that group instead of individual people. You can then add and remove people from the groups to provide access to only those that are allowed.
See More information about sharing with Groups at https://support.google.com/a/users/answer/9308872?hl=en