Peter works as a Network Administrator for the uCertify Inc. The company has a Windows-based network. All client computers run the Windows XP operating system. The employees of the company complain that suddenly all of the client computers have started working slowly. Peter finds that a malicious hacker is attempting to slow down the computers by flooding the network with a large number of requests. Which of the following attacks is being implemented by the malicious hacker?

A.
SQL injection attack

B.
Buffer overflow attack

C.
Denial-of-Service (DoS) attack

D.
Man-in-the-middle attack

Explanation:
A Denial-of-Service (DoS) attack is mounted with the objective of causing a negative impact on the performance of a computer or network. It is also known as a network saturation attack or bandwidth consumption attack. Attackers perform DoS attacks by sending a large number of protocol packets to the network. The effects of a DoS attack are as follows:
Saturates network resourcesn

Disrupts connections between two computers, thereby preventing communications between services
Disrupts services to a specific computerCauses failure to access a Web siteResults in an increase in the amount of spamA Denial-of-Service attack is very common on the Internet because it is much easier to accomplish. Most of the DoS attacks rely on the weaknesses in the TCP/IP protocol. Answer option A is incorrect. A SQL injection attack is a process in which an attacker tries to execute unauthorized SQL statements. These statements can be used to delete data from a database, delete database objects such as tables, views, stored procedures, etc. An attacker can either directly enter the code into input variables or insert malicious code in strings that can be stored in a database. For example, the following line of code illustrates one form of SQL injection attack:
query = “SELECT * FROM users WHERE name = ‘” + userName + “‘;” This SQL code is designed to fetch the records of any specified username from its table of users. However, if the “userName” variable is crafted in a specific way by a malicious hacker, the SQL statement may do more than the code author intended. For example, if the attacker puts the “userName” value as ‘ or ”=’, the SQL statement will now be as follows:
SELECT * FROM users WHERE name = ” OR ”=”;
.Answer option D is incorrect. Man-in-the-middle attacks occur when an attacker successfully inserts an intermediary software or program between two communicating hosts. The intermediary software or program allows attackers to listen to and modify the communication packets passing between the two hosts. The software intercepts the communication packets and then sends the information to the receiving host. The receiving host responds to the software, presuming it to be the legitimate client.
Answer option B is incorrect. Buffer overflow is a condition in which an application receives more data than it is configured to accept. It helps an attacker not only to execute a malicious code on the target system but also to install backdoors on the target system for further attacks. All buffer overflow attacks are due to only sloppy programming or poor memory management by the application developers. The main types of buffer overflows are:
Stack overflowFormat string overflow Heap overflow Integer overflow