Many people these days are taking advantage of the Windows 9x ability to network two or more computers and share files and printers easily. The problem is that file and printer sharing services function by turning any PC wanting to share its files into a file and printer server. When this trusting and sharing computer is connected to a network, this "service" is naturally extended and made available to the all the other computers which are also connected to the network. But when that network is THE INTERNET, suddenly your computer is literally offering its files to every other computer in the world!
So, if you want the safest and least costly method of protecting your system while on the Internet, turn off sharing on your computer. In Explorer, right click on your hard drive, go to Properties | Sharing, and select "Not Shared".
There is a way that you can still share files, and provide Internet security. That's to use file sharing, but with password protection. At the same screen as above, select "Shared As", enter a "Share Name", select "Full" Access Type, and enter a Full Access Password. This will give you some security while allowing file sharing on your local network.
Microsoft's networking technology is only required for sharing files and printer services with other Microsoft-based PC's. It is not needed for connecting to the Internet or for using any Internet services. Using it in wide area networking (WAN - like the Internet) situations, dramatically lowers your security by divulging information about you and your computer, exposing Microsoft's weak password protection system to password crackers over the Internet, bringing your machine to the attention of Internet scanners and intruders and making you a target for attack.
File sharing at it's basic level allows sharing resources over the full network your computer is attached to - both local area network and the Internet. However, advanced settings allow this sharing to be unbound - allowing it with some protocols (your local network) while blocking it on others(Internet).
For a full discussion, along with step-by-step instructions, go to:
Several commercial software packages are available, such as Symantec's $60. Norton Internet Security 2000. It contains software for creating a personal firewall, as well as AntiVirus software. When online, you're essentially logged on to a network within the Internet. The firewall blocks intruders several ways such as by protocol, IP address, port, or specific application. Other features make browsing less annoying: the utility prevents Java applets from loading, removes banner ads, halts pop-up browser windows, and blocks cookies.
A shareware program many have used, Network Ice's $40. BlackIce Defender (www.networkice.com)can be evaluated before purchase. It provides equal protection, is easier to use, and has extensive online tutorials about hacking attacks.
Cheaper still is Zone Labs' ZoneAlarm 2.1 (www.zonelabs.com), which is free for personal use. In many ways it's better than either of the other two, and, what the heck, you can't beat the price!