Section: A+ Essentials

11) What is true about a firewall? (Choose three.)

1. Block a hacker from accessing the network.
   
2. Restrict a user from accessing an unauthorized site.
   
3. Expose the identities of the user and the network.
   
4. Provide an alarm for unauthorized access attempts.
   
5. A firewall can only be implemented in hardware.
   
6. A firewall can only be implemented in software.
   

A firewall can greatly improve network security and reduce risks to hosts on the subnet by filtering inherently unsafe services. As a result, the subnet network environment is exposed to fewer risks, since only selected protocols will be able to pass through the firewall. A firewall also provides the ability to control access to site systems. For example, some hosts can be made reachable from outside networks, whereas others can be effectively sealed off from unwanted access. Privacy is of great concern to certain sites, since what would normally be considered innocuous information might actually contain clues that would be useful to an attacker. Some sites may also wish to block services such as finger and Domain Name Service. If all access to and from the Internet passes through a firewall, the firewall can log accesses and provide valuable statistics about network usage. A firewall, with appropriate alarms that sound when suspicious activity occurs, can also provide details on whether the firewall and network are being probed or attacked.

Exam Objective: 2.1 Apply and use common prevention methods.