What is a newsgroup? - Sarah Maher, Dublin 16

The newsgroup is among the oldest phenomena on the Internet. The first newsgroup emerged in 1979 when a couple of graduate students at a US university connected a few computers together to allow information about UNIX programming to be exchanged. This grew into a wider voluntary network, called Usenet, covering many topics.

Newsgroups differ from websites in that all the information published on them is put there by the users. If you have a question which you think someone somewhere in the world will know the answer to, you find the appropriate newsgroup and post your question.

A newsgroup is effectively a gathering of people who share an interest. Those people can be anywhere in the world, so they're especially useful if the topic you're interested in is unusual.

There are thousands of newsgroups covering every conceivable subject from music to religion to gardening to movies to history. As well as asking or answering questions, you can just post a comment. If you're curious to have a look but might not want to contribute anything yourself, don't worry: nobody will know you're there. You can just "lurk" around reading other people's comments.

Some newsgroups charge a fee, but most still adhere to the Internet's original spirit of free distribution of information. You should be aware that many websites now also have discussion forums, which are a limited version of what a newsgroup offers, so it's worth searching the web for your topic as well.

The main web browsers, Netscape Navigator and Internet Explorer, have built-in newsreader programs. Look under the Help menu in your browser for instructions. But the best place to start is probably Deja.com (go to www.deja.com/usenet), which allows you to use newsgroups through a web interface.

Is there a great danger of catching a virus like the one which was in the news last week? - Robert Flynn, Galway

Last week's much-publicised malicious virus was sent as an email attachment with the words "Kindly check the attached love letter from me!" to encourage the recipient to open the attachment. The virus only went into action if and when the attachment was opened.

If you receive an e-mail with an attachment you're not expecting, don't double click on the attachment. Either a) delete it without opening it, b) if possible ask the sender what it is or c) seek help. By the way, just because you have been sent something by someone you know does not mean it is safe - this virus, like others before it, spreads by forwarding itself to all the addresses in your e-mail address book.

In general you can't catch a computer virus by simply browsing the web, unless you download a programme and run it. Similarly, e-mail is safe unless you are sent an attachment. The most common way of catching a virus is by copying something from a floppy disk. Chances are your computer has an anti-virus programme which will scan your hard drive for viruses and delete them. Use it!

Send your WebWorld queries to webworld@ irishtimes.ie or by post to William Hederman, The Irish Times, D'Olier Street, Dublin 2.