buffer overflow

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buffer overflow

What happens when you try to store more data in a buffer than it can handle. This may be due to a mismatch in the processing rates of the producing and consuming processes (see overrun and firehose syndrome), or because the buffer is simply too small to hold all the data that must accumulate before a piece of it can be processed. For example, in a text-processing tool that crunches a line at a time, a short line buffer can result in lossage as input from a long line overflows the buffer and overwrites data beyond it. Good defensive programming would check for overflow on each character and stop accepting data when the buffer is full.

See also spam, overrun screw.

buffer overflow

A common cause of malfunctioning software. If the amount of data copied into a memory buffer exceeds the size of the buffer, the extra data will overwrite whatever is in the adjacent bytes, and those bytes could hold numbers and codes the program constantly uses (see flag and variable). It only takes an error of one bit to crash software.

Certain copy instructions transfer strings of data within memory until some character such as a null or return is reached, signaling its end. Such instructions are potentially dangerous and can be avoided by using instructions that copy a fixed number of bytes.

Buffer Overruns Are Exploited
If software is written to assume the correct amount of data will always be input and makes no provisions otherwise, malicious hackers can exploit this situation by entering more and more data until the computer crashes. When it does, the computer's registers are examined to find out if it was attempting to execute an instruction in the overrun buffer area and if so, the precise location. The exploit is then carried out by appending machine instructions at the end of the input that the computer will execute.

Slammer Wreacked Havoc
In January 2003, the Slammer worm on the Internet caused a billion dollars worth of damage. Using randomly generated IP addresses, Slammer used the buffer overflow exploit to replicate itself. Within three minutes after the first Slammer packet was unleashed, the number of infected computers was doubling every eight seconds. Within 15 minutes, large sections of the Internet were overloaded and out of commission. See buffer and buffer flush.
References in periodicals archive ?
execution as a result of buffer overflows, including the Microsoft RPC
against all types of buffer overflows, without any signature or code
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Entercept's generic protection against buffer overflow exploits would have prevented hackers from using this vulnerability to break into exposed systems.
They developed the necessary knowledge of Assembler, socket programming and the technical basis of a buffer overflow as part of their studies within this project.
With a multi-layered security solution including intrusion prevention, anti-virus and buffer overflow protection, ISS is the only security vendor that has been able to provide companies with effective protection for this vulnerability in the absence of a patch from Microsoft.
The exploit found in XP also affects XP Service Packs 1 and 2 and involves buffer overflows in USB device drivers.
WatchGuard's true Zero Day protection stops new and unknown threats such as viruses, spyware, Trojans and buffer overflows through its unique Intelligent Layered Security.
It provides comprehensive protection for Web servers against common Web application exploits like buffer overflows, command injection, and SQL injection.