Hackers are players who cheat and break rules using a Cheat Engine and/or other third-party hacking programs. Other players can easily report and possibly ban hackers by holding shift on the keyboard and clicking on the little brownish-yellow paper with an exclamation mark on the leaderboard. Then the member can type in how the player is hacking. Clicking submit will send the report. Sadly, after many false reports and many innocent people getting banned this feature was unplugged. The only ways to report hackers is to record the hacker in-game then report to a moderator via XGen Forums or go to a moderator (mainly flat world or 2-D) and tell them the game name and if needed server of the hacker(s).
Hacking is not recommended, and you will usually face a ip ban from the game ranging from 1 week to 5 years. Also, players can appeal their ban, but if they were permanently banned for hacking or for ranking by illegitimate means (e.g. afk ranking, instant respawn hack, suicide hack, etc...) your account's stats will be reset if moderators decide to unban you.