How to protect an application from code injection?

Question

Programming

Hello, how can I protect an application written in C ++.
I would like to know:

1. how you can detect and prevent the injection of someone else's code;
   
2. protect application data from reading / writing from outside;
   

Now to protect the application is used:

1. Checking hash sums of files received from the server;
   
2. Storage of important data with salt (magic number);
   

I would also be grateful for useful literature on writing "anti-cheat" and other auxiliary security utilities.
I don’t want to make a hybrid application (using C ++ and a virtual machine: lua, pawn, squerli, and others) - an additional waste of time and effort, in addition to debugging code twice as much.

Answer 1

You can try to imagine what exactly a cheat can do with the data, and build in a check to see if the data has been changed in an illogical way.
A kind of test built into the application itself. By the way, if you really periodically call a certain function with test data and compare the results with known ones, you can catch the moment when the function was changed and began to do something wrong or wrong. No hash checks etc.

Answer 2

There are many ways, from simple - hash verification, to verification of the number of lines or characters in the application.
More and more depends on the imagination.

Answer 3

In general, a difficult task ... Commercial protectors - I think it's an easy option.