LinkedIn surreptitiously uploads your contact list so they can spam your friends. They get potential for new users and you get negative karma. The best way to avoid this situation is to not use LinkedIn at all. Unfortunately, that's not an option in modern business world.

The first step is to be extremely vigilant when signing up or installing their app. The default is to upload your contact list and they try to hide the bypass button. But it is there and make sure you bypass contacts upload.

If you accidentally did this in the past, you can delete them. To delete an imported contact from your address book:

1. Click the My Network icon at the top of your LinkedIn homepage.
2. Click See all below Your connections on the left rail.
3. Click Manage synced and imported contacts near the top right of the page.
4. Select the Imported tab on the top of the page and check the box next to the contact you want to delete.
5. Click the Delete selected button near the bottom of the page.
6. If you're sure of removing the selected people from your contacts, click Delete selected contact in the popup window.