Let me show you how easy it is to discover confidential info
As we all know, Google indexes everything! Often times, we see this as a convenience, but there is a downside. Your documents and spreadsheets can be exposed to anyone who searches Google. You may find that hard to believe, so I'll let you try it for yourself. Copy the search phrase below and place it into Google.
intext:smtp | pop3 intext:login | logon intext:password | passcode filetype:xls | filetype:xlsx
Here is a more generic one
filetype:xls username password email
or some links to video cameras
There are many many more searches that can be done, all of which are considered passive reconnaissance. You can find many more search phrases over at the Google Hacking Database
It's best to store confidential documents in an encrypted resource, such as a Veracrypt encrypted volume.