A stack buffer overflow occurs when a program writes data to a buffer exceeding the allocated space, potentially corrupting other data and allowing malicious applications to take control. Mitigation strategies include address space layout randomization.
A stack buffer overflow is what happens when a program enters a computer’s memory longer than the allocated space. In some circumstances this can corrupt other data in memory, causing problems in the functioning of the computer. In other cases, a stack buffer overflow can be exploited by a malicious application to take control of other parts of the computer.
The name of a stack buffer overflow first comes from the stack, which is effectively an active list into which data is organized—the term comes from the analogy of the accumulation of physical elements. One version of this, the call stack, is the list a computer program uses to keep track of which various parts of the program, subroutines, are operating at any given time. Because the call stack operates on a temporary basis and needs to be accessed quickly, it is located in computer memory rather than in permanent storage such as the hard drive.
Since modern operating systems allow multiple programs to run simultaneously, it is necessary to organize the way memory is allocated, including the call stack. This is done efficiently by allocating buffers, a space in memory designed to be large enough to accommodate the maximum space required by a particular buffer. In most cases some of the space will be unused, so it acts as a buffer between data from different applications, leaving room to cope if you suddenly need extra space. One way to visualize this would be to think of a library that allocates a certain amount of space to each subject area, making sure to leave some extra space to cope if, say, all the books on a subject were in the library of the same subject. time, rather than any of them being controlled.
A stack buffer overflow occurs when a program writes call stack data to the buffer in a way that exceeds the allocated space. This can happen by mistake, usually through a bug in a program. For example, if an application is designed to allow the user to type in a phone number, but has no limit on the number of characters that can be entered, a hacker might be able to use the unlimited field to intentionally cause an overflow of the stack buffer. Depending on how the operating system works, this could allow the hacker to gain indirect access to another application or the operating system itself.
There are several approaches to mitigating the effects of a stack buffer overflow. One is known as address space layout randomization. This arranges the most important data areas on your computer randomly. The idea is that even if a hacker causes or exploits a stack buffer overflow, he won’t be able to reliably exploit the breach.
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