I have a spreadsheet with sensitive data. How might I block a certain column from others users viewing it?
UPDATE: Now is possible to block viewers to make a copy or download a shared spreadsheet. For details see Stop, limit or change sharing.
There is no way to securely block
One alternative for editors is to use two spreadsheets, one for sensitive data and another for non-sensitive data each of them with the proper access permissions.
NOTE: I'm working on an spreadsheet add-on that I hope to be able to release during September 2018.