The A+ Certification & PC Repair Handbook (Charles River Media Networking/Security)

The Internet is a huge network that connects millions of host computers with unique IP addresses, all over the world. It is the largest source of information available. The Internet offers a vast array of services: you can buy almost anything, see just about anywhere, and talk or chat with anyone who is connected.

Here are some important Internet-related terms that you should be familiar with for both of the A+ exams:

Uniform Resource Locator (URL): The URL is the line typically located at the top of the browser, such as http://www.charlesriver.com. The first part of the line is the Internet protocol to be used—for example, http:. The second part of the URL line is used for the Internet address you are trying to access. It can be an IP address or a domain name, such as charlesriver.com.

DNS (Domain Name System) server: This server or service converts fully qualified domain names to IP addresses and makes it possible for you to enter “charlesriver.com” into your Web browser instead of entering the 12-digit IP address.

Hypertext Transfer Protocol (HTTP): Internet protocol used to transmit instructions to the World Wide Web from a Web browser.

Hypertext Markup Language (HTML): HTML allows Web pages to be formatted with graphics and symbols other than plain text. HTML provides the Web page with a set of instructions pertaining to how the page should be displayed to the end user.

Extensible Markup Language (XML): XML is similar to HTML, but XML offers developers and designers more flexibility in creating Web pages through the use of call tags.

Viruses

A virus is a program or specific piece of code that is designed, when executed, to duplicate itself and/or spread itself to other areas of a system or other systems in a networked environment. In general terms, a virus will replicate itself until it uses up all available system resources, such as memory or hard drive space. The result of an undetected virus that has infected a system and has been successful at achieving its goal is a system that simply will not function. In most cases, this makes the system unavailable to other systems or results in a denial of service.

The Internet also offers a vast array of threats to you and your computer. You can lose your good credit standing if certain personal information is obtained and used for illegal purposes. Computers are vulnerable to computer viruses, as well as full-scale marketing attacks.

The Internet is swarming with many unfriendly computer viruses. A computer virus is a program or piece of code that is typically designed to store itself in your computer’s memory or on your hard drive. Most viruses make copies or duplicate themselves over and over until your memory or hard drive become inoperable. If you are interested in protecting the integrity of your stored data or the business you may be responsible for, it is very important to utilize a good virus protection program and update your antivirus .DAT files (definitions) on a regular basis. .DAT is the file extension used for a file or program that contains a list of the most current viruses. If you are running an enterprise network, you should incorporate a good enterprise antivirus solution. The top manufactures of antivirus software offer single-user or multi-user versions of their antivirus software programs. It is important to remember that computer viruses are most commonly obtained from the Internet and floppy disks.

Worms

A worm is a type of virus that gets its name from its inherent ability to spread itself to other networked systems, remain resident in memory, and keep in contact with other segmented pieces of itself until triggered by a certain event to duplicate and spread itself.

Most worm viruses reside in memory, unattached to files, and when triggered, will reproduce themselves until available resources are exhausted. A worm is a self-contained unit or program that is typically spread through e-mail attachments and network connections, such as drive mappings.

A worm is a type of virus that can replicate itself; however, worms do not attach to other programs. In other words, worms are not carried by or attached to hosting files.

Trojan Horses

A Trojan horse is a program that appears on the outside to be harmless. It masquerades itself as an apparently nondestructive, harmless, and innocent application, program, or message. Trojan horses can carry very dangerous payloads that are highly destructive to networks and systems.

Most Trojan horses are hidden in Internet attachments that oftentimes are distributed with e-mail in the form of jokes, love letters, and misguiding advertisements. One of the most important facts to understand about Trojan horses is that they do not replicate or copy themselves. They require actions by the user to activate and deliver their dangerous contents, such as the opening of an attachment or the running of an application. Worms and viruses duplicate themselves. Trojans do not.

Antivirus Practices

A combination of education, training, and management practices, along with the use of strong antivirus products, are essential to the survival and welfare of computer systems and networks.

There are some basic guidelines that should be followed when using and managing antivirus software at home or in a business enterprise:

• Install, update, and maintain reputable, quality antivirus software in servers and workstations. This includes setting up daily antivirus definition updates, enabling real-time protection, setting up scheduled scans of all system drives, and enabling e-mail and attachment scanning.

  Note

  If you are unable to install new software programs or device drivers on your system, your virus protection software or firewall may be blocking your install abilities. You may have to disable real-time protection or disable your entire antivirus suite altogether before installing new software. You should consult your antivirus manufacturer’s manual for protection and new installation instructions.

• All users of computer systems (at home or in the workplace) should be educated/alerted when virus attacks occur or are expected to occur. Symantec Corporation does a great job at updating their Web site when virus threats are anticipated. This information can prove invaluable to administrators who need to apply particular patches or make updates in preparation for new or anticipated variations of viruses.

• Educate all users (at home or in the workplace) that opening e-mail attachments as well as instant messaging attachments may be detrimental to your system’s life span.

• In a business environment, ensure that your corporate antivirus business policy is up to date and accurate. Ensure that new and existing employees sign an addendum that states they are familiar with the company’s policy regarding computer usage as well as virus policy and procedures.