Answer: D 

Explanation: 

Answer: C 

Explanation: 

DNS operates over TCP and UDP port 53. TCP port 53 is used for zone transfers. 

Answer: B 

Explanation: 

Mandatory Access Control allows access to be granted or restricted based on the rules of classification. MAC also includes the use of need to know. Need to know is a security restriction where some objects are restricted unless the subject has a need to know them. 

Answer: A,E 

Explanation: 

Joe wants to send a message to Ann. It’s important that this message not be altered. Joe will use the private key to create a digital signature. The message is, in effect, signed with the private key. Joe then sends the message to Ann. Ann will use the public key attached to the message to validate the digital signature. If the values match, Ann knows the message is authentic and came from Joe. Ann will use a key provided by Joe—the public key—to decrypt the message. Most digital signature implementations also use a hash to verify that the message has not been altered, intentionally or accidently, in transit. Thus Ann would compare the signature area referred to as a message in the message with the calculated value digest (her private key in this case). If the values match, the message hasn’t been tampered with and the originator is verified as the person they claim to be. This process provides message integrity, nonrepudiation, and authentication. A certificate authority (CA) is an organization that is responsible for issuing, revoking, and distributing certificates. A certificate is nothing more than a mechanism that associates the public key with an individual. If Joe wants to send Ann an encrypted e-mail, there should be a mechanism to verify to Ann that the message received from Mike is really from Joe. If a third party (the CA) vouches for Joe and Ann trusts that third party, Ann can assume that the message is authentic because the third party says so. 

Answer: C 

Explanation: 

The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate. An OCSP responder (a server typically run by the certificate issuer) may return a signed response signifying that the certificate specified in the request is 'good', 'revoked', or 'unknown'. If it cannot process the request, it may return an error code. 

Answer: C 

Explanation: 

Viewing confidential information on someone’s monitor is known as shoulder surfing. By moving their monitors so they cannot be seen, the executives are preventing users passing by ‘shoulder surfing’. 

Shoulder surfing is using direct observation techniques, such as looking over someone's shoulder, to get information. Shoulder surfing is an effective way to get information in crowded places because it's relatively easy to stand next to someone and watch as they fill out a form, enter a PIN number at an ATM machine, or use a calling card at a public pay phone. Shoulder surfing can also be done long distance with the aid of binoculars or other vision-enhancing devices. To prevent shoulder surfing, experts recommend that you shield paperwork or your keypad from view by using your body or cupping your hand. 

Answer: A 

Explanation: 

A replay attack (also known as playback attack) is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack by IP packet substitution (such as stream cipher attack). 

For example: Suppose Alice wants to prove her identity to Bob. Bob requests her password as proof of identity, which Alice dutifully provides (possibly after some transformation like a hash function); meanwhile, Eve is eavesdropping on the conversation and keeps the password (or the hash). After the interchange is over, Eve (posing as Alice) connects to Bob; when asked for a proof of identity, Eve sends Alice's password (or hash) read from the last session, which Bob accepts thus granting access to Eve. 

Countermeasures: A way to avoid replay attacks is by using session tokens: Bob sends a one-time token to Alice, which Alice uses to transform the password and send the result to Bob (e.g. computing a hash function of the session token appended to the password). On his side Bob performs the same computation; if and only if both values match, the login is successful. Now suppose Eve has captured this value and tries to use it on another session; Bob sends a different session token, and when Eve replies with the captured value it will be different from Bob's computation. Session tokens should be chosen by a (pseudo-) random process. Otherwise Eve may be able to pose as Bob, presenting some predicted future token, and convince Alice to use that token in her transformation. Eve can then replay her reply at a later time (when the previously predicted token is actually presented by Bob), and Bob will accept the authentication. One-time passwords are similar to session tokens in that the password expires after it has been used or after a very short amount of time. They can be used to authenticate individual transactions in addition to sessions. The technique has been widely implemented in personal online banking systems. Bob can also send nonces but should then include a message authentication code (MAC), which Alice should check. Timestamping is another way of preventing a replay attack. Synchronization should be achieved using a secure protocol. For example Bob periodically broadcasts the time on his clock together with a MAC. When Alice wants to send Bob a message, she includes her best estimate of the time on his clock in her message, which is also authenticated. Bob only accepts messages for which the timestamp is within a reasonable tolerance. The advantage of this scheme is that Bob does not need to generate (pseudo-) random numbers, with the trade-off being that replay attacks, if they are performed quickly enough i.e. within that 'reasonable' limit, could succeed. 

Answer: A 

Explanation: A spam filter is a software or hardware solution used to identify and block, filter, or remove unwanted messages sent via email or instant messaging (IM). 

Answer: D 

Explanation: 

Discretionary access control (DAC) allows access to be granted or restricted by an object’s owner based on user identity and on the discretion of the object owner. 

Answer: A 

Explanation: