It is a data integrity assurance software aimed at detecting and reporting
accidental or malicious changes to data.
The following answers are incorrect :
Nessus is incorrect as it is a vulnerability scanner used by hackers in discovering
vulnerabilities in a system.
Saint is also incorrect as it is also a network vulnerability scanner likely to be used by
hackers.
Nmap is also incorrect as it is a port scanner for network exploration and likely to be used
by hackers.
Reference :
Tripwire : http://www.tripwire.com
Nessus : http://www.nessus.org
Saint : http://www.saintcorporation.com/saint
Nmap : http://insecure.org/nmap

Explanation/Reference:
Availability is the opposite of "destruction."
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 59.

Section: Network and Telecommunications
Explanation/Reference:
The proxy (application layer firewall, circuit level proxy, or application proxy ) is a second generation firewall
"First generation firewall" incorrect. A packet filtering firewall is a first generation firewall.
"Third generation firewall" is incorrect. Stateful Firewall are considered third generation firewalls
"Fourth generation firewall" is incorrect. Dynamic packet filtering firewalls are fourth generation firewalls References:
CBK, p. 464
AIO3, pp. 482 - 484
Neither CBK or AIO3 use the generation terminology for firewall types but you will encounter it frequently as a practicing security professional. See http://www.cisco.com/univercd/cc/td/doc/product/iaabu/centri4/user/ scf4ch3.htm for a general discussion of the different generations.

Explanation/Reference:
Asynchronous Communication is the basic language of modems and dial-up remote access systems.
Source: KRUTZ, Ronald L & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 100.