In most newly released games, players find ways to exploit the game for their own benefit, and Halo: Reach is no exception.
These cheaters had been boosting for in game currency, or credits, by completing in game daily challenges and disconnecting from Xbox Live, which resulted in the cheaters getting credits but not completing the challenge. Thus, they could keep earning the credits.
However, Bungie has now taken action against approximately 15,000 cheaters by resetting all of their credits. In addition, the cheaters will have a one day ban for earning credits.
Bungie clearly means business, so it’s advised to not cheat, a standard rule of thumb when it comes to video games. Eventually, there WILL be consequences.