Buffer overflow (buffer overrun): An anomaly where a program, while writing data to a buffer, overruns the buffer’s boundary and overwrites adjacent memory locations, happen from improper coding when a programmer fails to perform bounds checking. Buffers are areas of memory set aside to hold data, often while moving it from one section of a program to another, or between programs. Buffer overflows can often be triggered by malformed inputs, if one assumes all inputs will be smaller than a certain size and the buffer is created to be that size, if an anomalous transaction produces more data it could cause it to write past the end of the buffer. If this overwrites adjacent data or executable code, this may result in erratic program behavior, including memory access errors, incorrect results, and crashes. By sending in data designed to cause a buffer overflow, it is possible to write into areas known to hold executable code, and replace it with malicious code.