Protection refers to the Spamcleaner feature located at the bottom of the user panel. It was created to help users delete unauthorized tweets posted from their accounts in periods of inactivity.
The feature is intended to be activated when you’re not using Twitter (because sleeping, in class, on vacation etc) but have your account available on Tweetdeck/Hootsuite for peers to retweet from it.
Now and then the common Tdeck/Hootsuite password is leaked to unaffiliated third parties (hackers) who can use it to mass retweet their own accounts or, worse, to make offensive/false statements on your behalf that can alienate followers and damage your reputation.
Because retweets are cleaned by spamcleaner, unauthorized tweets would normally remain on the timeline until the user deletes them. And if the user is offline for one reason or another while this happens, such unauthorized tweets can stay up for hours, even days triggering hostile attacks from nonfollowers and followers alike. With protection, on the other hand, unauthorized tweets would stay up for at most 10 minutes and the damage can be negligible.
To activate protection you have to set a time interval for which you want it to be on. The image below shows how to set protection for the next 4h (from 5am to 9am). You first set the starting time, to do so click on the from field, a calendar will appear with hours displayed on the right. Pick a time and do the same with the to field (end time). Now click on activate protection and you should see a green notification saying that the date range has been saved.
Now that protection has been activated all tweets posted in the saved time range will be deleted right after being posted. If you want to tweet before the saved end time (9am in the above example), all you have to do is click on the turn off protection button and new tweets won’t be deleted anymore.