Edward Elliot gives advice on how to deal with the two types of trouble on the Net: threats to security and threats to privacy.

The Internet is about as safe as a dark alley. Maybe there are bad guys lurking in the shadows; maybe there are not. But you aren't defenseless. Potential security bogies include viruses contained in file downloads, rogue ActiveX controls that can crash your computer, malicious e-mail attachments, holes in Java that let hackers read data on your hard disk and a host of other weaknesses in your Internet software. To ensure your privacy, or the safety of your computer, there are a few rules one should abide by.

Despite all the press reports, the odds are against you becoming the random victim of a hacker. But remember that the Web has a big population of fun seekers and bored surfers. It just takes one to upset your site by your leaving a small door open. If your site has any means of any "surfer inputs," then it is a doorway for a thrill-seeking surfer to have some fun.

What are "surfer inputs?" Guestbooks, classified ads or bulletin boards are the best examples of your granting a surfer the privilege of entering information on to your site. Guestbooks are not that dangerous, but classified ads and bulletin boards are because of the ability the Web master has to edit the pages. Keep this doorway locked and secure.

Rather than having your site hacked, you're much more likely to run into a virus. Installing and using anti-virus software should take care of this potential problem. One of the first rules of e-mail is don't open e-mail attachments from people you don't know. Not any more - the rules have changed. Just don't open any attachments at all because your e-mail buddy's computer could have a virus and it will pass it on to yours. What to do about these attachments? There is no real solution other than keeping your anti-virus software always up to date.

This rule applies whether on the Web or in the real world. Use good judgment about paying with credit cards. If you don't know if the company is reputable or don't know where to find it in the real world, then keep your card in your wallet.

Many Web sites actually are programmed to harvest information about any visitor who visits. They send small files called cookies to your hard drive. Each cookie can be read only by the Web server that created it, and it may be stored for up to days or months and read later when you revisit the site.

Among other things, cookies permit Web sites to track your name, your e-mail address, your ISP's name, the last site you visited, your operating system, and your browser's specific make and version number. They also can help you out by storing passwords so that you can get into subscription-only sites without having to type the password every time.

But the savvy consumer will want to control what information is being collected. You can have your browser refuse to accept any cookie or use a program such as Kookaburra Software's CookiePal to track and manage your cookies.

Information collected online can also be used in more sinister ways, such as sending you obscene e-mails. For example, every time you post to a Usenet newsgroup, your e-mail address becomes available to everyone who reads the group. And some newsgroup postings stick around for years. One way around this problem is to use an anonymous re-mailer service such as Replay, which forwards your e-mail without your address.

Whenever you enter your name, address and phone number in a form on the Web, that information could be going to people you don't know, so think twice before revealing personal data, especially your home address or your phone number.

For a complete rundown of security dangers on the Net - and an interactive security check - check out CNET's feature, "Net Crime: Don't Be a Victim." You can find it at http://coverage.cnet.com/Content/Features/Dlife/Crime/.

Threats to your privacy are more subtle, but here again you can define some limits. For instance, you can make your e-mail safe from prying eyes by using an encryption program such as Pretty Good Privacy (PGP). Encryption software translates your message into a secret code so that only the person who has the correct decryption key can read it - in other words, the person to whom you're sending it.

In the end, computer viruses can be cured by formatting and re-installing programs. Sites and computers can be fixed after hackers leave by re-installing programs. So the best protection is to have available a complete, up-to-date backup of your data.