You can find updates on the latest secret codes for "Moshi Monsters" on MoshiSecrets.com. Other types of cheats can be found at MoshiMonstersPlanet.com or SuperCheats.com.
The most prominent type of cheat for the game "Moshi Monsters" is found in the form of secret codes. These codes are built into the game, and frequently updated lists containing them can be found in many places online, including at moshisecrets.com/codes.
Other types of cheats, ones that fall under the category of exploits or bugs, can also be found online on websites such as supercheats.com or moshimonstersplanet.com. It should be noted, however, that these types of cheats are generally unreliable and unstable. The game developers may patch such exploits and bugs out of their game at any time, and thus they may not function as expected.
Additionally, extreme caution should be exercised when attempting to use exploits or bugs as cheats, as such methods can frequently corrupt saved games or account files. In the case of online games, such as "Moshi Monsters," using these sorts of cheats is usually a violation of the Terms of Service agreement you signed upon creating your game account. Such violations, if discovered, can lead to the offending account being banned from the game.