Right-click the connection on which you would like to enable ICF, and then click

Chapter 17 ✦ Using E-Mail use encryption with your e-mail messages, you must use digital IDs in conjunction with encryption. So the people in your address book must have a digital ID; you use their public key to encrypt the messages. When the recipient gets the message, his or her private key decrypts it. And so it goes, back and forth, between the two of you. Pretty Good Privacy PGP is a freeware program that uses public key authentication and encryption. PGP is a product of the PGP Corporation. Noncommercial U.S. citizens can obtain PGP from many Web sites, including http:web.mit.edunetworkpgp.html. MIT’s Web site contains PGP for a variety of platforms. For more information about PGP, see Chapter 22. Using virus protection Virus protection is most important with your e-mail program. E-mails with attachments come into your computer and your network and can damage and even destroy data and hardware. You should definitely use a firewall to help screen out viruses see Chapter 16, but you should also use an antivirus program on each computer attached to the network. Generally, viruses come in on the Internet or via e-mail. A virus could come in on a floppy disk brought from work or from your child’s school as well. So even if you don’t have an Internet account, you should protect yourself from viruses. You can choose from many antivirus programs. Rather than downloading a free copy an antivirus program, you would be much better served to purchase a copy of a program that is trusted and tested. Free antivirus programs do not usually let you update virus definitions to catch the latest threats. Plus, free programs are not as meticulous at scanning your computer and protecting it. Tip Viruses, worms, and Trojan horses Viruses come in different permutations, and they are constantly changing. Some people use the terms virus, worm, and Trojan horse interchangeably, but they are not the same thing. These pests are designed to cause problems by people who know a lot about programming and have nothing better to do with their time. ✦ A virus is a software program, script, or macro that propagates itself by infecting other programs on the same computer. Viruses can destroy or damage a computer, data, or applications. Or a virus can just pop up an annoying window and do no damage. True viruses cannot spread to another computer without your help, such as through trading files using a floppy disk or via an e-mail attachment. ✦ A worm is a type of virus; it also propagates itself. A worm, however, can gain access to the computer and travel across networks from one computer to the next, traveling on file-sending and -receiving features. It causes damage not only to the computer and soft- ware but also to the network by deleting or modifying the data. ✦ A Trojan horse refers to a program you think you want, such as a free game, but it con- tains something harmful. For example, you start the free game but find it erases every file in the directory. A Trojan horse could alternatively contain a virus or a worm, which then spreads the damage. Continued