CompTIA Security+ Question L-36

Which of the following types of attacks involves interception of authentication traffic in an attempt to gain unauthorized access to a wireless network?

A. Near field communication
B. IV attack
C. Evil twin
D. Replay attack

Answer: B

Explanation:
An initialization vector is a random number used in combination with a secret key as a means to encrypt data. This number is sometimes referred to as a nonce, or “number occurring once,” as an encryption program uses it only once per session. An initialization vector is used to avoid repetition during the data encryption process, making it impossible for hackers who use dictionary attack to decrypt the exchanged encrypted message by discovering a pattern. This is known as an IV attack. A particular binary sequence may be repeated more than once in a message, and the more it appears, the more the encryption method is discoverable. For example if a one-letter word exists in a message, it may be either “a” or “I” but it can’t be “e” because the word “e” is non-sensical in English, while “a” has a meaning and “I” has a meaning. Repeating the words and letters makes it possible for software to apply a dictionary and discover the binary sequence corresponding to each letter. Using an initialization vector changes the binary sequence corresponding to each letter, enabling the letter “a” to be represented by a particular sequence in the first instance, and then represented by a completely different binary sequence in the second instance.

WEP (Wireless Equivalent Privacy) is vulnerable to an IV attack. Because RC4 is a stream cipher, the same traffic key must never be used twice. The purpose of an IV, which is transmitted as plain text, is to prevent any repetition, but a 24-bit IV is not long enough to ensure this on a busy network. The way the IV was used also opened WEP to a related key attack. For a 24-bit IV, there is a 50% probability the same IV will repeat after 5000 packets.

CompTIA Security+ Question D-68

A computer supply company is located in a building with three wireless networks. The system security team implemented a quarterly security scan and saw the following.
SSIDStateChannelLevel
Computer AreUs1connected170dbm
Computer AreUs2connected580dbm
Computer AreUs3connected375dbm
Computer AreUs4connected695dbm
Which of the following is this an example of?

A. Rogue access point
B. Near field communication
C. Jamming
D. Packet sniffing

Answer: A

Explanation:
The question states that the building has three wireless networks. However, the scan is showing four wireless networks with the SSIDs: Computer AreUs1 , Computer AreUs2 , Computer AreUs3 and Computer AreUs4. Therefore, one of these wireless networks probably shouldn’t be there. This is an example of a rogue access point. A rogue access point is a wireless access point that has either been installed on a secure company network without explicit authorization from a local network administrator, or has been created to allow a hacker to conduct a man-in-the-middle attack. Rogue access points of the first kind can pose a security threat to large organizations with many employees, because anyone with access to the premises can install (maliciously or non-maliciously) an inexpensive wireless router that can potentially allow access to a secure network to unauthorized parties. Rogue access points of the second kind target networks that do not employ mutual authentication (client-server server-client) and may be used in conjunction with a rogue RADIUS server, depending on security configuration of the target network. To prevent the installation of rogue access points, organizations can install wireless intrusion prevention systems to monitor the radio spectrum for unauthorized access points.