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Obfuscate (hide) the PE imports from static/dynamic analysis tools.
Theory
This's pretty forward, let's say I've used VirtualProtect and I want to obfuscate it with Sleep, the tool will manipulate the IAT so that the thunk that points to VirtualProtect will point instead to Sleep, now at executing the file, windows loader will load Sleep instead of VirtualProtect, and moves the execution to the entry point, from there the execution will be redirected to the shellcode, the tool put before, to find the address of VirtualProtect and use it to replace the address of Sleep which assigned before by the loader.
How to use
It can be included directly as a library, see the following snippet (based on the example), also you can take a look at cli.cpp (https://github.com/d35ha/CallObfuscator/blob/master/cli/cli.cpp).
#include

int main() {
cobf obf_file = cobf("sample.exe");
obf_file.load_pe();
obf_file.obf_sym("kernel32.dll", "SetLastError", "Beep");
obf_file.obf_sym("kernel32.dll", "GetLastError", "GetACP");
obf_file.generate("sample_obfuscated.exe");
obf_file.unload_pe();
return 0;
}; Also can be used as a command line (https://www.kitploit.com/search/label/Command%20Line) tool by supplying it with the input PE path, the output PE path and optionally the path to the configuration file (default is config.ini).
cobf.exe [config file]
The config file contains the obfuscations needed (dlls, symbols, ...).
Here is a template for the config file content
; Template for the config file:
; * Sections can be written as:
; [dll_name]
; old_sym=new_sym
; * The dll name is case insensitive, but
; the old and the new symbols are not.
; * You can use the wildcard on both the
; dll name and the old symbol.
; * You can use '#' at the start of
; the old or the new symbol to flag
; an ordinal.
; * The new symbol should be exported
; by the dll so the windows loader can resolve it.
; For example:
; * Obfuscating all of the symbols
; imported from user32.dll with ordinal 1600.
[user32.dll]
*=#1600
; * Obfuscating symbols imported from both
; kernel32.dll and kernelbase.dll with Sleep.
[kernel*.dll]
*=Sleep
; * Obfuscating fprintf with exit.
[*]
fprintf=exit
Example
Build this code sample
#include
#include

int main() {
SetLastError(5);
printf("Last error is %d\n", GetLastError());
return 0;
}; After building it, this is how the kernel32 imports look like

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Now let's obfuscate both SetLastError and GetLastError with Beep and GetACP (actually any api from kernel32 will be ok even if it's not imported at all).
The used configurations are
[kernel32.dll]
SetLastError=Beep
GetLastError=GetACP Here is the output (also you can use the library directly as shown above).