A security administrator examines a network session to a compromised database server with a
packet analyzer. Within the session there is a repeated series of the hex character 90 (x90).
Which of the following attack types has occurred?

A.
Buffer overflow

B.
Cross-site scripting

C.
XML injection

D.
SQL injection

Explanation:
The hex character 90 (x90) means NOP or No Op or No Operation. In a buffer overflow attack, the
buffer can be filled and overflowed with No Op commands.
A buffer overflow occurs when a program or process tries to store more data in a buffer (temporary
data storage area) than it was intended to hold. Since buffers are created to contain a finite
amount of data, the extra information – which has to go somewhere – can overflow into adjacent
buffers, corrupting or overwriting the valid data held in them. Although it may occur accidentally
through programming error, buffer overflow is an increasingly common type of security attack on

data integrity. In buffer overflow attacks, the extra data may contain codes designed to trigger
specific actions, in effect sending new instructions to the attacked computer that could, for
example, damage the user’s files, change data, or disclose confidential information. Buffer
overflow attacks are said to have arisen because the C programming language supplied the
framework, and poor programming practices supplied the vulnerability.