Public hacks are typically poorly coded and released quickly to drive traffic to the coder's website. These hacks are easily detected and result in mass bans.
Private hacks are coded at a very professional level. Typically, instead of downloading the hack itself, you download a launcher. You then log in to the launcher using an account with which you purchased a subscription to the hack. The server verifies your account information and allows you to download temporary encrypted hack files which directly inject into the game and are removed from your computer upon exiting the game.
These hacks typically include anti-cheat countermeasures, and can detect when an anti-cheat client requests information from the user and responds by blocking the request or providing false information. This makes the hack virtually undetectable. However, in the event that a user is detected, the server immediately revokes every other user's access to the hack to prevent further detection until the coder can fix the detection issue.
The hacks are also designed to prevent users from sharing access to the hack by logging the first user's hardware ID. If another user attempts to access the hack (or even the same user on a different computer), the program detects the different HWID and locks the account.
Private hacking communities are relatively small compared to the public communities and a game's playerbase in general, so it's not worth a developer's time and money to try and battle the private coders, despite the fact that they have the most effective hack software.
