Here are a few possible reasons why a name you don't recognize might show up as a viewer, commenter, or editor on an item you own:You shared your file with a mailing list.
If an individual from the mailing list opens your document, spreadsheet, presentation, or drawing, they will show up by name in the list of people currently viewing the doc.
If you share a file with someone who doesn't have a Google Account, the invitation email can be forwarded to other people. When they click the link in the forwarded invitation, they'll be able to access to your doc.
This happens because Google Drive can’t verify access by a particular email address unless it’s an email address associated with a Google Account. In this case, access to the sharing invitation is the authorization that Google Drive uses for a person to access a file.
If you think this may have happened, mouse over the name of the person you don't recognize; the name of the person (or email list) whose invitation that person used will be displayed.
The default setting in Google Docs, Sheets, and Slides lets editors of an item add other viewers and editors to that item. You can turn off this ability when you share your item. If you think another person with access to your item shared it with someone you don't know, you can ask the other people with editing access to your item. You can also remove someone's editing rights at any time.
If someone changes the display name associated with their email account, they'll still have access (they're the same person, after all!), but they may appear to be new and different. Hover over their name in the sharing settings to see their email address.
If a document is set by the owner to be viewable or editable by everyone, then Google Drive doesn't show the names of those who choose to view or edit the item. Google Drive displays only the identities of people who are explicitly given permission to view or edit an item (either individually or as part of a group).
People who are not given explicit access are labeled Anonymous user.
When anonymous viewers or editors might show up
The owner doesn't explicitly share an item with any individuals, but chooses the sharing option ‘People can view this item without signing in.’
- All viewers or editors will appear as anonymous.
The owner allows anyone with the link to view or edit the item, but also explicitly shares the document with some specific viewers or editors.
- The people who were explicitly given access will appear by name if they view or edit the item.
- Other users with access will appear as anonymous when they view or edit the item.
Using Google Apps for your business, school, or domain? People accessing documents within their own domain will always show up by name, whether they've been given individual access or they've been added as part of the entire domain. However, if you set a document to be viewable by anyone both within and outside of your domain (if you don't require sign-in to view the document), people outside your domain will show up as anonymous users when they view or edit the document. The domain administrator can control whether documents may be shared outside the domain using the control panel.