Buffer Overflow Vulnerabilities in Programming. Exam Practice Questions and Answers with Complete Solution. Chapter 10
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Course
Computer information systems
Institution
Computer Information Systems
Define buffer overflow. - Answers A condition at an interface under which more input can be placed into a buffer or data holding area than the capacity allocated, overwriting other information. Attackers exploit such a condition to crash a system or to insert specially crafted code that allows them...
Buffer Overflow Vulnerabilities in Programming. Exam Practice Questions and Answers with Complete
Solution. Chapter 10
Define buffer overflow. - Answers A condition at an interface under which more input can be placed into
a buffer or data holding area than the capacity allocated, overwriting other information. Attackers
exploit such a condition to crash a system or to insert specially crafted code that allows them to gain
control of the system.
List the three distinct types of locations in a processes address space that buffer overflow attacks
typically target. - Answers stack, heap or data section of a process
What are the possible consequences of a buffer overflow occurring? - Answers corruption of data used
in the program, unexpected transfer of control in the program, memory access violations, eventual
program termination
What are the two key elements the must be identified in order to implement a buffer overflow? -
Answers Identification of a buffer overflow vulnerability that can be triggered using externally sourced
data under the attackers control
Understanding of how that buffer will be stored in the process memory and hence the potential for
corrupting adjacent memory locations and potentially altering the flow of execution of the program.
What types of programming languages are vulnerable to buffer overflows? - Answers Assembly
languages and C and its derivatives.
Describe how a stack buffer overflow is implemented. - Answers A stack buffer overflow occurs when
the targeted buffer is located on the stack, usually as a local variable in a function's stack frame. The
exploits include an unchecked buffer overflow resulting from the use of the C gets() function. The
program tries to put more data into a byte array than it is allowed to hold, thus overwriting parts of the
adjacent memory.
Define shellcode. - Answers The act of transferring the execution to code supplied by the attacker that is
often saved in the buffer being overflowed is known as shellcode. (Traditionally its function was to
transfer the control to a command-line interpreter.)
What restrictions are often found in a shellcode, and how can they be avoided? - Answers Shellcode has
to be position independent, cannot contain any NULL values. The first can be avoided using a tricky
combination of CALL instructions to obtain the actual position. The second is avoided by using the XOR
function of a register value with itself to generate zero values as the code runs.
Describe what a NOP sled is and how it is used in a buffer overflow attack. - Answers This a mechanism
to determine the starting address of the code the attacker wants to execute. The attacker can exploit
the fact that the code is often much smaller than the space available in the buffer. By placing the code
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