Lecture 3 of Computing Security 1 Course for 4th class

Lecture 3 overview:
• Security Attacks
• Security Mechanisms
• A Model for Network Security
8. Security Attacks: General Introduction
it has become essential to protect useful information from malicious
activities such as attacks. Attacks are typically categorized based on the
action performed by the attacker. An attack, thus, can be passive or
active.
Passive Attacks: The main goal of it is to obtain unauthorized access to
the information. For example, actions such as intercepting and
eavesdropping on the communication channel can be regarded as
passive attack. These actions are passive in nature, as they neither affect
information nor disrupt the communication channel. Passive information
attack is thus more dangerous than stealing of goods, as information theft
may go unnoticed by the owner.
Figure (5): Passive Attack.
Computing Security 1 Lecture 3
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Active Attacks: involve changing the information in some way by
conducting some process on the information. For example,
• Modifying the information in an unauthorized manner.
• Initiating unintended or unauthorized transmission of information.
• Alteration of authentication data such as originator name or
timestamp associated with information.
• Unauthorized deletion of data.
• Denial of access to information for legitimate users (denial of service).
Figure (6): Active Attack.
Cryptography provides many tools and techniques for implementing
cryptosystems capable of preventing most of the attacks described above.