Buffers are a type of memory storage area that holds data temporarily while it is being moved from a location to a new destination. Buffer overflow, sometimes referred to as buffer overrun, happens when the volume of data being transferred exceeds the available storage capacity of the dedicated memory buffer. When this occurs, instead of writing the data to the buffer it instead overwrites memory location adjacent to it.
An example of this is when a buffer used for login credentials has been designed to expect password and username inputs of around 8 bytes. If a transaction includes credentials of a higher byte size, like 10 bytes, the computer program may potentially write the excess 2 bytes data past the buffer’s boundary.
Such buffer overflows can impact all kinds of software. They are typically the result of either a failure to provide adequate space or a malformed input. However, if the transaction ends up overwriting executable code, the result can be a program behaving unpredictably and generating memory access errors, incorrect results, and even crashes.
Defining a buffer overflow attack
Threat operators exploit buffer overflows by overwriting an application’s memory. This can effectively alter the execution path of an app, triggering a specific response that can either damage data files or expose confidential information. For instance, a hacker may introduce additional code, that sends new instructions to the app in order to gain access to an enterprise’s IT systems.
If threat actors understand an application’s memory layout, they can then intentionally feed the amount of input they know the buffer is incapable of storing. As a result, they can overwrite areas used to hold executable code and replace it with some of their own. For instance, a hacker can overwrite an object that is pointing to another memory area and instead direct it to an exploit payload so they can assume control over the application.
What are the different kinds of buffer overflow attacks?
The most common type of attack is a stack-based buffer overflow attack. These assaults leverage stack memory that is only in existence during a function’s execution time.
The second type of buffer overflow threat is a heap-based attack. These are less common as they are harder to conduct. Heap-based attacks involve flooding specific memory space allocated for an application beyond the memory used for its current runtime functions.
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