A Memory Leak Attack is a subtle but serious threat that targets how a computer system manages memory. Let’s unpack it clearly and thoroughly.

🧠 What Is a Memory Leak?

A memory leak occurs when a program allocates memory but fails to release it after it’s no longer needed. Over time, this causes the system to run out of usable memory, leading to performance degradation, crashes, or system instability.

💣 What Is a Memory Leak Attack?

A Memory Leak Attack is a type of Denial-of-Service (DoS) attack where an attacker intentionally triggers or exploits memory leaks in software to drain system resources.

Two Main Variants:

1. Triggering Existing Leaks:

   • The attacker repeatedly performs actions that cause a known memory leak in the target application.
   • Over time, memory usage grows until the system slows down or crashes.

2. Injecting Malicious Code:

   • In more advanced scenarios, attackers inject code that causes memory to be allocated but never freed.
   • This is more common in systems vulnerable to remote code execution.

🧪 Example Scenario

Imagine a web server that allocates memory for each incoming request but forgets to free it afterward. An attacker could:

• Send thousands of requests.
• Each request leaks a bit of memory.
• Eventually, the server runs out of RAM and becomes unresponsive.

📉 Impact of a Memory Leak Attack

🛡️ How to Defend Against It

• Code Auditing:

  • Regularly review code for proper memory management.
  • Use tools like Valgrind or AddressSanitizer to detect leaks.

• Limit Resource Usage:

  • Use OS-level controls (e.g., ulimit, cgroups) to cap memory per process.

• Patch Vulnerabilities:

  • Keep software updated to fix known memory leak bugs.

• Monitoring Tools:

  • Use system monitors to detect abnormal memory usage patterns.

🧰 Languages Most at Risk

Languages like C and C++ are especially vulnerable because they require manual memory management. In contrast, languages like Java, Python, and C# use garbage collection, which helps—but doesn’t eliminate—the risk.

Here’s a simple example of a memory leak in C to illustrate how it happens and why it’s dangerous.

🧪 Sample Memory Leak in C

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

int main() {
    while (1) {
        int *leak = malloc(sizeof(int) * 1000);  // Allocate memory
        // No free(leak); — memory is never released!
        printf("Allocated memory...\n");
    }
    return 0;
}

🧠 What’s Happening Here?

• malloc() allocates memory for 1000 integers.
• The pointer leak holds the address of that memory.
• But the program never calls free(leak), so the memory stays allocated.
• The loop runs forever, continuously allocating more memory.
• Eventually, the system runs out of RAM, and the program (or even the OS) may crash.

🛡️ How to Fix It

Simply add free(leak); after you’re done using the memory:

int *leak = malloc(sizeof(int) * 1000);
// Use the memory...
free(leak);  // Release it!

🔥 How Attackers Might Use This

An attacker could:

• Send repeated requests to a vulnerable server that leaks memory per request.
• Cause the server to allocate memory without releasing it.
• Eventually crash the server or degrade its performance.