JNTU B.Tech IV INFORMATION SECURITY Previous Question Paper (September - 2021 - R15)

Security attacks are broadly classified into two main categories: Passive Attacks and Active Attacks. These are further distinguished by whether the attacker attempts to alter system resources or merely observe information.

1. Passive Attacks

Passive attacks involve monitoring transmissions to gain information without altering the data or affecting system resources. These attacks are difficult to detect because they do not leave a trace on the communication channel.

• Release of Message Contents: The attacker intercepts sensitive data, such as emails or file transfers, to read the contents. Example: An unauthorized party eavesdropping on an unencrypted network connection to capture passwords.
• Traffic Analysis: The attacker observes the pattern, frequency, and length of messages to infer the nature of communication, even if the content is encrypted. Example: Monitoring the timing of encrypted traffic to determine when a company is communicating with a specific server.

2. Active Attacks

Active attacks involve modifying the data stream or creating a false stream. These are easier to detect than prevent, as they cause observable changes to the system or data.

• Masquerade: An entity pretends to be a different authorized entity to gain extra privileges. Example: An attacker using a stolen session token to impersonate an administrator.
• Replay: The attacker captures a valid data transmission and retransmits it later to produce an unauthorized effect. Example: Capturing a legitimate bank transfer request and re-sending it to trigger a second deduction.
• Modification of Messages: A portion of a legitimate message is altered, delayed, or reordered. Example: Changing the recipient or amount field in an intercepted financial transaction.
• Denial of Service (DoS): The attacker prevents or inhibits the normal use or management of communication facilities. Example: Flooding a web server with excessive requests so that legitimate users cannot access the service.

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