Therefore math overflows and the sign will be changed. Though this code successfully compiles but will produce an unexpected result as -155536 because such addition is too big a number to fit in 15 bits. What happens when the calculation 25000 + 25000 is done? Let's consider the following code snippets and conceive about the output? If the computer is being direct to store the number in a short integer type. Integer overflow or boundary condition results when the numeric data type designated to handle an operation fails to handle the data when input extends beyond the limit for that data type and eventually produce an unexpected outcome. Therefore, if 16- bit signed data type assigned a value of 60,000 then an integer overflow would definitely occur and program behave in an unexpected way. The 16-bit data type can only store a maximum value of 32,767, whereas a 32-bit data type can store a maximum value of 2,147,483,647. With 15 bits, 32768 (2 ^ 15) numbers can be represented. The high-order bit indicates whether the number is positive or negative. Furthermore, in case of signed short data representation, the leftmost zero signifies the high-order but in the signed short data depiction as following. Similarly, the short integer type is a signed data type that holds 2 bytes worth of data as illustrated in the figure above in which each zero represents one bit in this unsigned short data representation. Unsigned integer, on the other hand, is positive by default because it does not consume MSB bit at all.

Significant bit (MSB) of their first byte where 1 represents to Positive value and 0 is for Negative value. Signed integer store either a 1 or 0 in the most Furthermore, it has the ability to determine that the store value is either a positive or negative number by categorizing it into Signed and Unsigned. Second, don't trust inputs, always validate incoming buffers to make sure that buffer in correct size instead.Īn integer is a data type in programming that can hold numeric values and does not support fraction form. Hence as a buffer overrun defense, it is highly suggestive, never ever run code with elevated privileges unless you need it so. Also, attackers could only add user accounts if the code that contains the buffer overflow is running with high privileges. Hackers, in this quest, manipulates the program behavior in its own determined goals. The motive behind this vicious attack is to change the flow of execution in the application. As an analogy, if your code allocates 'n' bytes for a buffer, and your code copies more than 'n' bytes to the buffer then the buffer will overrun and your program yields strange result. However, buffer overflows issues are quite a rate as high-level languages does not have direct access to memory.

Buffer overrun and integer overflow issues are two aspects of the same coin in some extent, in fact, group with 'overflow' where malicious code try to be executed beyond the allocated buffer size without acquaintance of program in elevated privilege scenario.

Buffer overrun takes place when the input is larger than the space allocated for it, and memory is written outside the space allocated for it.

Integer overflow example