Microsoft has started banning users from Xbox Live who have pirated the leaked Halo 4. This doesn't come as a surprise considering it's obviously illegal and Microsoft did the same when Halo 3 leaked online.
Users on Reddit first reported that Microsoft's Live Enforcement team is sending out emails to pirates stating that they have been permanently banned from Xbox Live due to "illegitimate prerelease title play".
In a statement to EuroGamer, Microsoft said,
No matter how eager you're to play Halo 4, it really isn't worth the risk of a console ban as Microsoft is known for its strict rulings and it's highly unlikely that you'll be unbanned. Halo 4 will be officially released on November 6th.