Windows long strings instead of usernames in folder security tabs

I've noticed recently that an unsettling large number of users permissions settings are giving permissions to long strings rather than users.

My thought is the user was removed and all that remains is their GUID string or something, but I was just curious what might be causing this.

I'm not a big fan of seeing weird things considering the most I do is disable accounts, not delete them altogether.

 

Exactly.

Since you just took over, it's probably the old admin.

I generally disable the account for about a month, and if no one gripes, it gets deleted later. But then again, we have a high turnover rate and almost everyone has the same access rights. The previous admin was pretty good about using groups, too, so it wasn't a nightmare to take over.