PLEASE everyone ..... set your default posts as Friends ONLY. It is difficult to set this on some portable devices, so do it at home so your smart phones default to it as well.
It must be remembered that the purpose of Facebook is sharing so turning off settings so that you cannot see other people's comments would just give you a blank screen or just your posts .....
One of the things that we do that does cause over sharing issues is to LIKE, COMMENT or SHARE another person's post. This leaves control of the visibility to the person making the original post. I have noticed that a "few" of my friends and family sometimes post to the world (global) and if I LIKE or SHARE or COMMENT that post, it also goes on my timeline with that setting. ALL I can do is Remove or Unlike my action. It is a good idea to check the audience before making a post or responding to a post, in ANY way.
Do not Directly "respond" to anything that is "shared" to you. All the security issues are carried with it.
If you REALLY want to share a picture or idea, copy the content to your hard drive and then re-post. If it is a picture use a picture capture program. If it is text copy it to a TEXT editor (not a Word Processor) such as NotePad. Viruses can be hidden in text and pictures and this would ensure you do not spread them.
This provides more information and details about security and sharing ....
Hope it helps you all to be safe.