Viruses, Worms, and Trojan Horses

Transcription

1 Viruses, Worms, and Trojan Horses Be a Power Reader Make Personal Connections As you read this article, think to yourself, How can I apply this knowledge? How will what I m learning be useful to me? You may already know some things about computer viruses and how to prevent them. As you go along, create a brief outline of the topics covered. You can use the article s headings as a guideline for the outline. When you have finished, go over your outline. Which of these topics do you think will be most useful to you? Why? Try to apply your new knowledge to your everyday life. Introduction Do you know the answer to the question What do viruses, worms, and Trojan horses have in common? Well, they can all make our lives pretty miserable. These are computer programs that attack our computers without our even being aware of it. Some of these programs simply display a message, such as You have been attacked or Have a nice day. Others can slow down our computers and even destroy files stored on our hard disks. Catching a Virus A virus is a computer program that secretly stores itself on a disk or attaches itself to another file. It then repeatedly makes copies of itself. This process is called replication. The copies then attach themselves to other files. When a computer contains a virus (for example, on its hard disk), we say that the computer is infected. Some viruses become active when you use that file. Other viruses may become active on a certain day. For example, in 1988 the Jerusalem virus appeared. It is activated every Friday the 13th. Any files that you use on that day will be erased from the computer s hard disk. The year 2000 saw the I Love You virus appear. This virus spreads by attaching itself to messages. These messages are then sent to all the people listed in your address book. Because it was spread automatically by , it quickly infected tens of millions of computers. Worming through the Network Did you know that on January 24, 2003, a new kind of worm invaded our world? When it first began spreading, it multiplied so fast that its numbers doubled every 85 seconds. Only 10 minutes after this worm began, it had infected over 75,000 computers. Computer people around the world were afraid their systems would be attacked, for this was the kind of worm that infects computers. It became known as the Sapphire, or Slammer, worm. A worm is a malicious program one that has been created with the intent of causing harm that can replicate over and over. It is different from a virus because it does not infect other files. As you know, a network is a group of computers that are attached to one another. Messages (such as 76 TechCONNECT Online: Technology Foundations Copyright Glencoe/McGraw-Hill

2 s) and other information can be shared among these computers. The most common way that worms spread is over networks. This includes the Internet. They worm their way through the network. Once it gets started, a worm can replicate itself so fast that it can be impossible for the network to do any of its regular work! All of its energy is used up by the worm. The Sapphire/Slammer worm kept many computer networks from doing their regular work. Airlines had to cancel flights. In some places, it even interfered with elections. The damage it did was in the hundreds of millions of dollars. Watching Out for Gift Horses Do you know the story of the Trojan horse? Many people think this story is a legend, but regardless of whether or not it is true, it still has a lesson to teach us. In about 1300 B.C., the Greeks were fighting a battle against the city of Troy. The Greeks kept attacking the city s walls, but were unable to get inside. Then, they came up with a plan. They built a huge wooden horse with a hollow belly. Greek soldiers hid inside the horse s belly. The horse was given as a peace offering to Troy. The citizens of Troy took the horse inside their city. That night, while the people of Troy were sleeping, the Greek soldiers climbed out of the horse and took over Troy. Likewise, in computer lingo, a Trojan horse is a file that pretends to be a good program that wants to help you. For example, it may come to you as a free game or music. However, hidden inside is a malicious program that can damage your computer. This program might mangle your files so that they are unreadable or erase them from your hard disk. One Trojan horse, named PWSteal.Trojan, was able to steal users passwords, such as those used to access the Internet. Some of these passwords were then used for illegal purposes. A Trojan horse is different from a virus because it does not replicate itself. Even so, these programs can do a lot of damage. Protecting Yourself We all know that there are ways we can protect ourselves from colds and the flu for example, by washing our hands frequently. There are also ways that you can reduce your chances of catching a computer bug. Here are some tips to keep your computer free of viruses and other bad programs. Make certain that you have an antivirus application installed on your computer. Also make sure that the application is up-to-date. Companies that develop antivirus applications also provide frequent updates. These updates protect your computer from new viruses. Be careful when opening files that are attached to s. Only open the file if you trust the person who sent it to you. If you are unsure about what an attachment contains, you can always the person who sent it to you and ask him or her where he or she got it. Remember the old saying: Better safe than sorry. Be careful when downloading files from the Internet. Is the source one with which you are familiar? Don t download any files unless your antivirus application is working. Make backup copies of your files on a regular basis. It is a good idea to do this at least once a week. If your files are damaged by a virus, you can use these backups to replace them. Copyright Glencoe/McGraw-Hill TechCONNECT Online: Technology Foundations 77

3 AntiVirus Software Your best protection against viruses and similar programs is an antivirus application. Think of these applications as vaccinations for your computer. They protect your computer s health just as the measles vaccination you have received protects you from catching the measles. Two popular antivirus programs are Norton AntiVirus and McAfee VirusScan. Both of these applications will protect your computer from tens of thousands of viruses. Norton AntiVirus Antivirus applications can be set so that they constantly keep an eye on your computer, watching for any suspicious activity. They also can be set to automatically check your incoming for viruses. You can get antivirus software in the same way as you would get most other commercial software by purchasing it at a store or by buying it online. It typically comes on a CD-ROM so that you can install it on your computer s hard disk. Some companies also provide online antivirus software. You go to the company s Web site and enter a credit card number. You can then install the software directly onto your computer s hard disk. All commercial antivirus applications are updated frequently. These updates provide protection against viruses that have just been discovered. A dialog box may pop up once a month to remind you to go to the antivirus company s Web site to get the most recent updates. Typically, you simply click a button and the updates are downloaded onto your hard disk. Remember: new viruses are coming out all the time. It is very important to keep your antivirus application up-to-date. If an antivirus application finds a virus, it will attempt to erase the virus. The application will then tell you whether the virus has been removed. At any rate, you should immediately tell the person who sent you the infected file. That person will need to check his or her computer for viruses. Firewalls Many of us keep personal information on our computers. Some people use their computers to keep track of their bank accounts. Our hard disks may contain our credit card numbers so that we don t have to enter them each time we wish to make an online purchase. If an outsider uses the Internet to access our computer, he or she may be able to locate this information and use it to steal from us. Accessing a computer without authorization (particularly for illegal reasons) is called hacking. You may have heard about hackers who ve illegally accessed government computers and obtained secret information. Other hackers have stolen credit card numbers and used them to buy things. For many of us, our computers are most vulnerable when we are on the Internet. Special applications have been developed to protect us from hacking while we are on the Internet. These are called firewalls. Traditionally, firewalls have been used in large buildings such as apartment houses. They are special fireproof walls. If a fire starts in one apartment, the firewall 78 TechCONNECT Online: Technology Foundations Copyright Glencoe/McGraw-Hill

4 attempts to stop it from spreading to the next one. Likewise, firewall applications protect us from the dangers of the Internet. Two popular firewall applications are McAfee Personal Firewall Plus and Norton Personal Firewall. These programs will usually tell you if an outsider is trying to access your computer. They then stop that person from gaining access. McAfee Personal Firewall Plus Review Questions 1. Explain the difference between a virus and a worm. 2. Remember the legend of the Trojan horse in the Greeks battle against Troy. Explain how the malicious Trojan horse computer file works and why this is a fitting name for it. 3. List three things that can help protect your computer against viruses. 4. Has the widespread use of the Internet made it easier or harder for viruses and worms to spread? Why? 5. What is the purpose of a firewall? What Do You Think? 1. Have you (or has somebody you know) ever had any experiences with viruses? Describe what happened. 2. Your family has just purchased a new computer. You will be able to use it to access the Internet. What kinds of applications do you think you will need to protect your computer? 3. Last week, a student created a worm that slowed down your high school s network to the point where the school s computers could not be used. Nobody was able to conduct research or use the computers for three days until the worm could be removed. What do you think would be a fair punishment for the person who created this worm? Why? Copyright Glencoe/McGraw-Hill TechCONNECT Online: Technology Foundations 79

5 Glossary computer program A list of instructions that a computer can execute (carry out). Often called a program for short. firewall An application that prevents an outsider from accessing your computer over a network such as the Internet. hacking Accessing a computer without authorization, often for illegal purposes. network Computers that are linked together so that they can share messages, software, hardware, and so forth. The Internet is an example of a network. replication The process of making a copy of oneself. Trojan horse A file that pretends to be a good program, but actually has a malicious program hidden within it. For example, it may come to you as a free game or music; however, hidden inside there may be a program that can cause damage to the files on your computer. virus A computer program that replicates itself. These copies are stored on a computer s disk or attach themselves to other files. Some viruses cause damage (such as erasing files) while other simple display messages or graphics. worm A malicious program that multiplies over and over. Worms are typically spread over networks and are different from viruses because they do not infect other files. 80 TechCONNECT Online: Technology Foundations Copyright Glencoe/McGraw-Hill