Firewall

- A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.
Basically, a firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.
There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain name and Internet Protocol addresses. For mobile users, firewalls allow remote access in to the private network by the use of secure logon procedures and authentication certificates.
A number of companies make firewall products. Features include logging and reporting, automatic alarms at given thresholds of attack, and a graphical user interface for controlling the firewall.
Computer security borrows this term from firefighting, where it originated. In firefighting, a firewall is a barrier established to prevent the spread of fire.

 Reference:
William R. Cheswick, Steven M. Bellovin, Aviel D. Rubin (2003). "Google Books Link". Firewalls and Internet security: repelling the wily hacker

What actions must be taken in response in a security incidents?

In response, We should develop well in advance of any incidents,Documents all details of a security incidents.
We should have a public awareness campaign so that people will know of  what is the best thing to do.

What are some characteristics of common computer criminals including their objectives?

The common Computer criminals are the 1.)Hackers who test limits of the system and gain publicity.2.)Crackers who cause problems steal data and corrupt system.3.)Malicious Insiders usually due to weaknesses in internal control procedures and Disrupt companies Information System.4.)Industrial Spy Gathers Information available to the public andCaptured trade secrets and gaincompetetive advantage.5.)Cyber Criminals Hack into corporate computer and steal, and To reduce the potential for online credit cards fraud sites.6.)Cyber Terrorist Intimate or coerce governments to advance political or social objectives, and Launce computer base attacks.

Why has there been a dramatic increase in the number of computer related security incidents in recent years?

Computer related  security incidents increases because computer users was increases