In object-oriented programming, race conditions occur due to the sharing of common variables among object instances, which could be verified within the program code. For each file access, the program should be written to verify that the file is free before opening it and to check for object-in-use errors.
Core-file manipulation is another example of a race condition where a program or process enters into a privileged mode before the program or process has given up its privileged mode. If an attacker successfully manages to compromise the program or process during its privileged state, then the attacker has won the race.
14. What do most effective security controls over remote maintenance ports include?
a. Legal contracts and dial-back systems
b. Dial-back systems and modem pools
c. Legal contracts and modem pools
d. Dial-back systems and disconnecting unneeded connections
14. c. Remote maintenance ports enable the vendor to fix operating problems. The legal contract with the vendor should specify that there be no trap doors and that any maintenance ports should be approved by both parties. Modem pools consist of a group of modems connected to a server (e.g., host, communications, or terminal). This provides a single point of control. Attackers can target the modem pool, so protect it by installing an application gateway-based firewall control. Dial-back security controls over remote maintenance ports are not effective because they are actually authenticating a place, not a person. It is good practice to disconnect unneeded connections to the outside world, but this makes it difficult for a maintenance contractor to access certain ports when needed in an emergency.
15. Which of the following statements is not true about Internet firewalls?
a. A firewall can enforce security policy.
b. A firewall can log Internet activity.
c. A firewall can limit an organization’s security exposure.
d. A firewall can protect against all computer viruses in PCs.
15. d. Firewalls (also known as secure gateways) cannot keep personal computer viruses out of a network. There are simply too many types of viruses and too many ways a virus can hide within data. The most practical way to address the virus problem is through host-based virus-protection software and user education concerning the dangers of viruses and precautions to take against them. A firewall enforces the site’s security policy, enabling only “approved” services to pass through and those only within the rules set up for them. Because all traffic passes through the firewall, the firewall provides a good place to collect information about system and network use and misuse. As a single point of access, the firewall can record what occurs between the protected network and the external network. A firewall can be used to keep one section of the site’s network separate from another section, which also keeps problems in one section isolated from other sections. This limits an organization’s security exposure.
16. In a distributed computing environment, system security takes on an important role. Two types of network attacks exist: passive and active. Which of the following is an example of a passive attack?
a. Attempting to log in to someone else’s account
b. Installing a wiretap on a network cable to generate false messages
c. Denying services to legitimate users
d. Sniffing a system password when the user types it
16. d. A passive attack is an attack where the threat merely watches information move across the system. However, no attempt is made to introduce information to exploit vulnerability. Sniffing a system password when the system user types it is an example of a passive attack.
The other three choices are incorrect because they are examples of active attacks. Active attacks occur when the threat makes an overt change or modification to the system in an attempt to take advantage of vulnerability.
17. Use of preshared keys (PSKs) in a wireless local-area network (WLAN) configuration leads to which of the following?
1. Dictionary attack
2. Rainbow attack
3. Online attack
4. Offline attack
a. 1 and 2
b. 1 and 3
c. 2 and 3
d. 2 and 4
17. a. Dictionary attack is a form of guessing attack in which the attacker attempts to guess a password using a list of possible passwords that is not exhaustive. Rainbow attacks occur in two ways: utilizing rainbow tables, which are used in password cracking, and using preshared keys (PSKs) in a WLAN configuration.
The use of PSK should be avoided. In PSK environments, a secret passphrase is shared between stations and access points. The PSK is generated by combining the WLAN’s name and service set identifier (SSID) with a passphrase and then hashing this multiple times. Keys derived from a passphrase shorter than approximately 20 characters provide relatively low levels of security and are subject to dictionary and rainbow attacks. Changing the WLAN name or SSID will not improve the strength of the 256-bit PSK.
An online attack is an attack against an authentication protocol where the attacker either assumes the role of a claimant with a genuine verifier or actively alters the authentication channel. An offline attack is an attack where the attacker obtains some data through eavesdropping that he can analyze in a system of his own choosing. The goal of these attacks may be to gain authenticated access or learn authentication secrets.
18. Which of the following extensible authentication protocols is not secure?
a. EAP-TLS
b. EAP-TTLS
c. MD5-Challenge
d. PEAP
18. c. The MD5-Challenge is a legacy-based extensible authentication protocol (EAP) method along with a one-time password and generic token card, which are not secure. Although one-time passwords are generally considered secure by themselves, they are not that secure when they are used in conjunction with a generic token because the token could have been duplicated, fake, lost, or stolen.
The MD-5 Challenge is based on the challenge-handshake authentication protocol (CHAP), which is not a secure protocol. The other three choices are a part of the transport layer security-based (TLS-based) EAP methods, which are very secure.
19. Web content filtering software is related to which of the following?
a. Web bug
b. Blacklisting
c. RED
d. BLACK
19. b. Web content filtering software is a program that prevents access to undesirable websites, typically by comparing a requested website address to a list of known bad websites (i.e., blacklisting). Blacklisting is a hold placed against IP addresses to prevent inappropriate or unauthorized use of Internet resources.
The other three choices are not related to the Web content filtering software. Web bug is a tiny image, invisible to a user, placed on Web pages in such a way to enable third parties to track use of Web servers and collect information about the user, including IP addresses, host name, browser type and version, operating system name and version, and cookies. The Web bug may contain malicious code. RED refers to data/information or messages that contain sensitive or classified information that is not encrypted, whereas BLACK refers to information that is encrypted.