People also say "remove it, it's an injector", but an injector is the tool .exe to load an hack, that read/write in the memory, this tool dont have any exe and u can find some guide on how to activate it on nvidia site.I think this tool doesn't write the memory
Well, an injector is a piece of code which injects codes or a pattern of bits into memory or links parts of code into running code. To do that you can choose between different methods. One used by hacks is to change pointers on the running code to have your code run or you can simply make sure that the program which should be changed loads the new code parts you want by it self. For the last you can integrate you own dll's (Dynamic-link library).
The tool has a setup exe which places different files which are not included in BF3 in the BF3 folder(s) and one is a dxgi.dll. And i would guess it includes the code to have the FXAA filters loaded where BF3 does not use them or change the ones BF3 has included.
You can find some information about FXAA here:http://developer.download.nvidia.com/assets/gamedev/files/sdk/11/FXAA_WhitePaper.pdf
And you can also find some BF3 FXAA related information directly at the DICE side:http://publications.dice.se/attachments/GDC11_DX11inBF3_Public.pdf
as Johan Andersson presented this on the GDC in 2011.
So what is the result?
This tool changes the way DICE might use FXAA. So it changes the game and the visual effects. The author of the tool has listed "BlueShift, FogColor, Defog" besides others as visual changes.
Do you play better, aim better or have any advantage compared to players with out-of-the-box BF3 visuals?
I don't know. But reducing fog or change it colors is something i personally place in one line with other not meant visual changes, and so i personally don't like it in an online match.
If Evenbalance is looking at the code i'm sure they are building there opinion about how deep the changes are and if they open a way for more changes by others 3rd party tools utilizing this 3rd party dll introduced by that tool.
I have to note, this are my theoretically thoughts as i haven't used that tool or have it decompiled.
All informations here can be found using the web. One source is a forum of a german PC gamer magazin:http://extreme.pcgameshardware.de/battlefield-serie/189991-fxaa-injector-danoc1-fuer-battlefield-3-update-danoc1-v1-3-beta-download.html