There's a new glitch that allows you to lock a public match so you could have some fun with your friends or boost at your own risk. Here is how its done.

1. Search for the game type you want to lock.
2. Quickly leave the search.
3. Go to COD TV and go to friends feed.
4. Press A on the first video that's on films and it will say

Do you want to go to Theater?

5. Hover over Yes and press A + B at the same time.

Now you'll be in a lobby that no one could join besides the people you invite.

Note: If someone else is doing the glitch there's small chance that they'll get placed in your lobby. But you'll be able to play 3-4 games before someone joins you.
If you have a slow connection you need to press B a few seconds after A if you have a fast connection press A+B at the same time!