A gamerscore correction occurs on a player's LIVE account when they gain achievements through avoiding game play and the use of external tools. LIVE is committed to keeping the service free of this type of behavior as it violates the LIVE Terms of Use. When abnormal achievement or gamerscore activity is found, LIVE modifies the gamerscore of players who meet specific and automated criteria.
A LIVE player who obtained their gamerscore in this abnormal way will:
- Find their gamerscore reset to zero, and
- Be unable to regain all previously earned achievements, and
- Be labeled as a "cheater" for the community to view.
While players who have been identified by these criteria will start from a zero gamerscore, they will still be able to gain achievements for future games. In other words, we give them another chance to earn future achievements by earning them as other "fair" players do. The original gamerscore correction will remain permanent without any way to appeal.
Read more at the official Xbox.com
Gamerscore FAQ