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What Is a Buffer Overflow Attack and How Do You Prevent It?

Tristen Cooper

busy IT team

Cybercriminals have been exploiting buffer overflow vulnerabilities for over 35 years as a way to access vulnerable servers or web applications. One of the oldest examples of a buffer overflow attack is the Morris worm, which was first released in 1988 and impacted approximately 10% of devices connected to the internet at that time.

While buffer overflow attacks are not new, they’re still a significant digital threat that all developers need to be aware of. These attacks are particularly dangerous for programs written in C or C++ languages, as these languages are older and don’t have built-in protection for buffer overflow problems.

In this article, we’ll take a closer look at what buffer overflow is and how hackers exploit it using buffer overflow attacks. We’ll also discuss ways to identify and prevent buffer overflow attacks.

Key Takeaways

  • Buffer overflow happens when your system’s buffer receives more data than it has available space for.
  • In a buffer overflow attack, hackers exploit buffer overflow to enter executable code, compromise the data in the buffer, and ultimately gain access to the system.
  • Buffer overflow attacks are often difficult to detect, and they can result in the compromisation of secure data or even damage to your systems.
  • Programs written in C or C++ are most vulnerable to these attacks, as they don’t have safeguards in place to prevent them.
  • Implementing ASLR while writing code and using systems with data execution prevention help to prevent buffer overflow.

What Is Buffer Overflow?

Software programs and computer systems use buffers to process data as it moves from one place to another. Think of a buffer as a waiting room for data before it reaches your screen.

One place where we often notice buffers in action is while watching our favorite streaming services. The streaming service will send small upcoming sections of the video to the buffer as you’re watching, which keeps the video playing smoothly.

However, if you watch the show faster than the server can send video to the buffer, you’ll experience a buffering pause while it loads. This is just one example of the many ways that our computers use buffers to transfer information.

Buffers have a limited amount of memory space. Buffer overflow happens when the user input is higher than the buffer’s available space. When this happens, the extra data overflows into adjacent memory spaces, which can cause the entire program to malfunction. Buffer overflow issues often result in system crashes, denial of service, or incorrect output.

What Is a Buffer Overflow Attack?

Buffer overflow attacks happen when hackers leverage buffer overflow on a software program or operating system to compromise or access secure data. While buffer overflow attacks have been around for a long time, hackers are still using them – 59 new buffer overflow attacks were identified between January and March of 2021 alone. 

In the worst-case scenarios, cybercriminals can use buffer overflow attacks to access highly valuable financial or consumer data and compromise your business’s reputation. These attacks will also crash your website and server, resulting in lost sales and unhappy customers.

During these cyberattacks, hackers will use the buffer overflow to overwrite important memory locations and change the code execution. By feeding new code into the system, the hacker uses the buffer overrun to take control of the application or server.

Types of Buffer Overflow Attacks

There are a few different types of buffer overflow attacks. Each of these attacks uses different methods, but they all serve the same purpose of exploiting a buffer overflow to compromise server or application security.

Stack-Based Buffer Overflow

Stack-based buffer overflow attacks are the most common form of buffer overflow attack. In this attack, the hacker will send more data to the system than is allocated for the buffer, which corrupts the entire data stack. This attack only uses buffer stack memory that exists for the function the system is currently running, rather than the broader memory “heap”.

To gain control of the system, the hacker will insert malicious code into the data sent to the stack. This code then allows them to change the output of the program. They can use this to change credentials, access sensitive data, or cause a complete system shutdown.

Heap-Based Buffer Overflow

Heap-based buffer overflow attacks are less common than stack-based ones, as they are more difficult for hackers to carry out. However, they are just as dangerous and will cause serious security vulnerabilities for their targets.

In a heap-based buffer attack, the hacker floods a program’s entire memory space. This goes beyond just the runtime memory space that is flooded during a stack-based attack. The hacker will then use malicious code to corrupt and overwrite the data, gaining control of the application.

Integer Overflow Attack

Integer overflow attacks exploit numerical limits in a system to cause an overflow and ultimately gain access to a program. Computers make a variety of mathematical calculations while they are running. In an integer overflow attack, the hacker will use a numerical input that’s larger than what the system can handle.

This ultimately causes these mathematical calculations to run incorrectly, which then causes the system to malfunction. The hacker will then use these malfunctions to exploit the system and gain access.

Format String Attack

Format string attacks are another cybersecurity threat that use incorrect data input to overwhelm and compromise a server or application. While not technically a type of buffer overflow attack, these attacks work similarly and cause similar security compromises, and they’re very important to consider in the software development process.

In a format string attack, the hacker inputs data that causes the application to process the input incorrectly. This creates vulnerabilities that the hacker can exploit to destabilize the program and access vulnerable data.

Unicode Overflow Attacks

This is a very specific type of buffer overflow attack in which the hacker uses Unicode characters instead of ASCII characters. Unicode is a character coding standard designed to make international characters accessible on computers and mobile devices. By inserting Unicode characters into a program that is only designed to process ASCII characters, the hacker causes a buffer overflow and manipulates the system.

Who is Most Vulnerable to a Buffer Overflow Attack?

Programs written in the C and C++ languages are most vulnerable to buffer overflow attacks. These are some of the oldest programming languages in use, and due to their age, they don’t have any functions that prevent external uses from overwriting or accessing data. Any servers or applications that use these languages will need to take extra precautions to prevent buffer overflow attacks.

Alternatively, newer programming languages are much less vulnerable to buffer overflow attacks. This is because they were written after the earliest buffer overflow attacks and were developed with preventative safeguards in place. Java and Python are two examples of languages that are designed to minimize the opportunity for buffer overflow attacks.

How to Detect a Buffer Overflow Attack

Since buffer overflow attacks can have such devastating consequences, your team should always be on the lookout for them. The earlier you detect a buffer overflow attack, the better chance you will have at resolving the problem effectively and preventing long-term damage to your organization. Here are steps to take to detect a buffer attack.

Look for Unusual Activity

Certain types of unusual activity in your system could be indicative of an overflow buffer attack. For example, if you notice that your system is crashing more often than normal, malfunctioning in strange ways, or isn’t responding correctly to input, it might be a sign of a buffer overflow attack.

Even if this isn’t ultimately a sign of an attack, watching for and identifying this unusual activity gives you the opportunity to address other problems and inefficiencies in your system.

Check Your System Logs

Every computer has system logs that record all activity. You can use these system logs to your advantage to spot buffer overflow attacks. Learn how to check your system logs periodically and look for unusual activity. In particular, look for failed login attempts and strange inputs or commands, which could be a sign that something is amiss.

Leverage Cybersecurity Tools

Many cybersecurity tools and operating systems have features to identify and prevent buffer overflow attacks. Be sure to watch for notifications and alerts and address them quickly to mitigate problems.

For example, Microsoft Windows has a data execution prevention feature, which protects malicious actors from launching code in places they shouldn’t. Linux also has some mitigation features in place.

Additionally, an antivirus program may notify you of a buffer overflow attack if it is connected to a specific virus. However, antivirus programs do not prevent all buffer overflow attacks, so they shouldn’t be used as a prevention strategy on their own.

Bring in Experts

Even if your team is very diligent, you still might miss a buffer overflow exploit of your systems if you haven’t experienced one before. If you’re working in a language that is vulnerable to buffer overflow attacks or have noticed unusual malfunctions with your system, it’s worth bringing in an outside cybersecurity expert to help.

A cybersecurity firm can assess your systems to look for signs of a buffer overflow attack and put security measures in place to stop it. Working with a third-party cybersecurity firm also reduces stress on your in-house IT team to help you work more efficiently.

How to Prevent a Buffer Overflow Attack

Buffer overflow attacks are often tricky to catch. However, there are many steps you can take to prevent buffer overflow attacks from happening in the first place. Here are some things you can do to minimize these security threats.

Use Safe Programming Languages

As previously mentioned, some programming languages are more prone to buffer overflow attacks than others. When possible, avoid working in C or C++ and opt for Python, Java, Perl, or another secure coding option if you’re starting from scratch.

Implement ASLR

While building your systems, use address space layout randomization, or ASLR, to reduce the chances of a buffer overflow attack. This technique makes it very difficult for the hacker to figure out which areas of memory their code is executed in, ultimately making buffer overflow attacks very difficult.

Use A Compiler

If you’ve been writing in C, C++, or another vulnerable language and have been struggling with buffer overflow attacks, running your code through a compiler can help you prevent them. A compiler is a type of software that translates code from one programming language into another. Using a compiler means you can run your system in a safer language without having to rewrite all the code.

Turn On Data Execution Prevention

If you’re working in Microsoft Windows, make sure to have data execution prevention turned on. You’ll need to do this through your advanced system settings, as it doesn’t turn on automatically.

Conduct Regular Code Audits

Buffer overflow attacks often happen as a result of coding mistakes. To prevent this, conduct regular code audits as you’re working. Having the entire team review the code gives them a chance to catch mistakes the original programmer overlooked. It’s also important to provide ongoing support and education to help your team write the best code possible.

Update Your Software Programs

Failing to update your software programs in a timely manner will leave your organization vulnerable to a wide variety of security issues, including buffer overflow attacks. Schedule time to install updates and patches for software programs as they are released to avoid making your system a target.

Limit User Permissions

Keep in mind that buffer overflow attacks can come from someone within your organization as well as an outside attacker. To mitigate internal security risks, limit user permissions for your team based on the work they are doing.

While team members should have enough access to do their jobs, they should never have unchecked access, regardless of their rank within the organization. Additionally, it’s important to consider who has physical access to your servers and why to prevent these internal attacks.