What is Buffer Overflow? Prevention and Types of Buffer Attacks

Imagine you're filling a bucket of water and trying to fill more than it can hold. 

Of course, it overflows, doesn't it? 

The concept of buffer overflow is similar. It is one such cyber attack that can cause irreversible damage. 

This is why it's important to have protection and cyber security practices in place. Distributed denial of service (DDoS) protection tools help secure applications and prevent DDoS attacks. Let's explore the concept of buffer overflow and why it is essential to have DDoS protection software. 

Buffer overflows are often the result of a lack of input validation, where the program does not check the length or format of the data written to the buffer. A buffer overrun can allow attackers to inject their data into the buffer and leads to overwriting critical data or the execution of malicious code.  This potentially causes the system to crash or be taken over by the attacker, becoming a threat to application security and software development. 

The attacker can set a new value to the location where the exploited function is positioned, thus altering the process execution path. This can cause the program using the buffer to crash or execute arbitrary code. Attackers can gain access to the computer, network, or memory allocation to force crashes or security vulnerabilities that allow them to take control of the affected system. 

How does a buffer overflow attack work

The attacker typically uses a combination of specially crafted input data and malicious code to exploit vulnerabilities in the targeted system's software. The malicious code manipulates the buffer, thus, overflowing and allowing the attacker to execute this code.

To carry out a buffer overflow attack, the attacker first identifies a vulnerable system or software application and creates a payload of data designed to exploit the vulnerability. A network or a web-based attack vector, such as malicious websites or emails, delivers the payload. 

The target system receives the payload and processes the software application, which attempts to store the incoming data in the buffer. If the buffer is not large enough to accommodate the data, it will overflow and allow the code to execute as intended.

The attacker can then gain control of the system and potentially steal sensitive data, disrupt operations, or gain access to additional systems on the network. It is essential to regularly update software applications and implement security measures such as firewalls and intrusion detection systems to prevent buffer overflow attacks.

Buffer overflow attacks in the past

Before learning about the types of buffer overflow attacks, let's look at some popular incidents of buffer attacks from history.

• One of the first computer worms to receive a sizable amount of mainstream media attention was the November 2, 1988, Morris worm, now known as the Internet worm. The Morris worm attack exploited several vulnerabilities, including UNIX sendmail (using backdoor), finger (through a buffer overflow), and rsh/rexec. Additionally, it was able to guess weak passwords.
• In November 2014, the Sony Pictures Entertainment company suffered a major breach of its computer systems caused by a buffer overflow attack. The attackers stole sensitive information, including unreleased films and personal data of employees and celebrities.
• In June 2011, Citigroup bank suffered a buffer overflow attack that gave hackers access to the personal information of over 200,000 customers, including their names, addresses, and account numbers. The attackers used this information to steal over $2.7 million from the bank.
• The developers of Libgcrypt issued a security patch update in January 2021 after they discovered a severe heap-based buffer overflow vulnerability in the software. The bug would allow attackers to write arbitrary code and target machines. This buffer overflow was discovered by a Google Project Zero researcher. 

Types of buffer overflow attacks

Depending on the programming language and operating system (OS), there are different techniques to exploit buffer overflow vulnerabilities. The attacks are categorized based on the location of the buffer in the process memory. Some types of buffer overflow attacks are as follows.

Stack-based buffer overflow

A stack holds data in a last-in, first-out (LIFO) manner. A stack buffer overflow is a continuous memory space used for data organization associated with function calls, parameters, local variables, and management information. It’s empty until the target program requires user input, such as a password or username. The program then writes a return memory address to the stack. The user’s input is placed on top of the stack. After processing the stack, the user input is sent to the return address specified by the program. 

A stack has a finite size, and a developer must reserve some space for the stack. If the user input is longer than the stack space, the program cannot verify it and thus overflows., The overflow can become a security threat or loophole when combined with malicious inputs.

Heap-based buffer overflow attack

A heap is a memory structure used to manage dynamic memory. Developers use a heap to allocate memory whose size is unknown during compile time, and the amount of memory is too large to fit on the stack. A heap overflow attack floods the memory space reserved for a program and is challenging to exploit. They are rarer than stack attacks.

Integer overflow attack

Programming languages generally define a maximum size for integers. Exceeding this size can cause an error or return an incorrect result within the integer length limit. When using an integer in an arithmetic operation and the result value exceeds the maximum size of the integer, this causes an integer overflow attack. Let’s say that 8 bits of memory are required to store the value 192. During the process, if 64 is added to the base value, it adds up to 256. This value doesn’t fit in the allocated memory space since it would require 9 bits of memory.

Format strings overflow attack

In a format string attack, the attacker changes how an application flows. They do so by misusing string formatting library functions, such as printf or sprintf, to manipulate memory spaces.

Unicode overflow attack

A Unicode overflow attack exploits the memory required to store a string in the Unicode format rather than the American Standard Code for Information Interchange (ASCII) characters. Attackers use this type of buffer overflow attack when the program expects all inputs in ASCII characters. 

How to prevent buffer overflow attacks

To prevent buffer overflows, programmers must validate input properly and ensure that buffers are large enough to hold the expected data. Additionally, security measures such as data execution prevention (DEP) and address space layout randomization (ASLR) can help protect against buffer overflow attacks. Let’s look at a few measures to prevent buffer overflow: 

• Using an OS runtime protection makes it harder for attackers to conduct a buffer overflow attack successfully. 
• Address space layout randomization, or ASLR, helps arrange the positions of critical areas of a process. It includes the position of the heap, stack, and libraries. 
• DEP ensures that areas are either marked as executable or not executable and prevent an attacker from executing instructions written to an area via a buffer overflow. 
• A structured exception handling overwrites protection and blocks any attack using the stack-based buffer overflow. 
• Keeping devices patched ensures the discovery of buffer overflow vulnerabilities. However, it’s important to take safety measures between the time the security patch is created and deployed.
• Following the principles of least privilege (POLP) reduces the chances of a buffer overflow attack since users and applications have the permission required to do their jobs or perform essential tasks. 
• Use a language that does not allow buffer overflows, such as Java or Python.
• Use input validation and sanitization to ensure that user-supplied data does not exceed the allocated memory space for a buffer.
• Use secure coding practices, such as checking the bounds of arrays, to prevent overflows.
• Use security tools like firewalls and intrusion detection systems to monitor for and prevent buffer overflow attacks.
• Keep systems and software up-to-date with the latest security patches and updates to prevent exploitation of known vulnerabilities.
• Educate employees and users on the risks of buffer overflow attacks and the importance of following security best practices.

DDoS protection software

Distributed Denial of Service or DDoS attacks are a type of cyber attack in which numerous computers, often compromised by malware, are used to send a large volume of traffic to a targeted website or network to overwhelm and disrupt regular traffic. DDoS protection software is security software designed to protect against DDoS attacks.

DDoS protection software identifies and filters malicious traffic from legitimate traffic, allowing the targeted system to function normally. Several types of DDoS protection software are available, including cloud-based, on-premise, and hybrid solutions that combine the two. Some DDoS protection software includes features like website firewall protection and intrusion prevention.

Companies should invest in cyber security measures such as DDoS protection to help prevent cyber attacks. Every company has different needs, and choosing the right software for your company will help stay better prepared. Here is a software grid to help choose from the best in the market. 

Protect your digital assets 

Despite these precautions, buffer overflows can still occur. Therefore, organizations need robust cybersecurity measures to detect and respond to these attacks in time. Such measures can include regular security assessments, network traffic monitoring, and incident response plans to contain and remediate any attacks quickly.

Overall, buffer overflows are a serious threat to digital security. Organizations can protect themselves and their sensitive data by implementing proper input validation and security measures from the consequences of a buffer overflow attack.