LocalSize(0)

Created the Thursday 29 April 2021. Updated 1 year, 7 months ago.

The function LocalSize retrieves the current size of the specified local memory object, in bytes. By setting the hMem parameters with 0 will trigger an exception in a debugger that can be used as an anti-debugging mechanism.


Technique Identifier

U0128

Technique Tag

localsize


Code Snippets

#include <iostream>
#include <windows.h>

using namespace std;

int main()
{
	SIZE_T s;
	printf("Starting the LocalSize()\n");
	for (int i = 0; i < 0xFFF; i++){
	    s = LocalSize(0);
	}
	printf("Sempai! :) \n");
	return 0;
}

Detection Rules

rule Detect_LocalSize: AntiDebug {
    meta: 
        description = "Detect LocalSize as anti-debug"
        author = "Unprotect"
        comment = "Experimental rule"
    strings:
        $1 = "LocalSize" fullword ascii
    condition:   
       uint16(0) == 0x5A4D and filesize < 1000KB and $1
}
rule:
  meta:
    name: trap debugger with localsize
    namespace: anti-analysis/anti-debugging
    author: lordtmk@protonmail.com
    scope: basic block
    examples:
      - B67E5B1985742F62785122B637EF4FBD:0x4B1F5B
  features:
    - and:
      - api: LocalSize
      - mnemonic: push 
      - number: 0

Additional Resources

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