External vs Internal Hacks

Hey all,
I was wondering which hacks can be done on the client side, and which are only external. Obviously aimbots and such can be made client side, and changing gametypes, prestige lobbies etc are external.
More specifically, unlocking all weapons and attachments, although it could be done through a lobby which would help anyone unlock everything, but could it be done locally as well? In other words, can local hacks be considered external hacks that will only apply to your particular client?
I suppose the next question would be, where do I begin? I have a fair amount of experience in both c# and c++ so language isnt a particular restriction, however I am most interested in client side modifications. Could someone post a link to a client hack tutorial?

All help would be appreciated

MPGH's Community has a thriving source of experienced coders & tutorials curtailed for hacking .

Please click this link to check out some cool tutorials which may help you out in your projects: http://www.mpgh.net/forum/forumdisplay.php?f=161

Hacks such as Prestige Hacks and Level Hacks/ Unlocks are usually client to server interactive. With the case of MW2, the hack changes your stats on the servers .

Games such as Call of Duty 4, have a local file where all your stats are saved as Profiles.

Client side hacks would be ESP (Hitboxes), AImbots, SIlent Bots, Fullbright, No Sky, No Flash etc which modify only your client game by injecting code with a graphical overlay over DirectX Graphical game outputs, thus showing executing the coded menu/hack you injected locally. It does not affect the server by any means but rather use the Client sided info to modify your gameplay outputted by the soldier.

I hope this helped you. And in Modern Games, level hacks are more of a server sided thing rather then a saved stats file on your PC.