Spam is tinned, processed luncheon meat, originally produced by Hormel Foods of Minnesota. It's made from pork shoulder, ham and various spices.

It acquired its moniker after the company's founder, Jay C Hormel, sponsored a naming competition back in 1937. The prize-winner, Kenneth Daigneau, won $100 for the now infamous brand label.

What's that? You thought we'd be writing about that junk mail scourge of the internet? Ah, you must be thinking of spam.

Hormel doesn't mind the name of its billion-selling foodstuff being used to describe the junk that clogs your inbox, but it does insist on the correct capitalisation when referring to its product. So, SPAM is what you eat, spam is what you delete.

There are two types of spam. The first plagues internet newsgroups in the shape of a message that's repeated or posted an unacceptable number of times. The content of the message, whether it's on-topic or not, is irrelevant.

Newsgroup spam rarely contains anything pertaining to the group in which it appears, and serves only to interrupt genuine messages.

The other type of spam is the one that afflicts email - unsolicited messages that offer everything from unrepeatable business opportunities to miracle cures or pornography.

Email spam is sent in bulk using mailing lists. Despite its tailored appearances, it's never personal.

At best, spam is an annoyance; at worst, it costs money. Downloading anything from the internet takes time, and if you pay your ISP for phone calls, you're paying to download messages you don't want.

Spam costs ISPs too; transmitting it wastes space on ISP servers, which in turn bumps up operating costs. Who foots the bill for that? We do.

Although some US states have passed legislation against spam, the UK hasn't. UK ISPs are in favour of opt-in legislation; if people want spam, they ask for it.

Unbelievably, there is support for opt-out legislation, where companies can spam freely until they're asked not to.

Computeractive is campaigning against spam, but until spam is regulated, all you can do is avoid it. If you want to know how to do that, read on.

The basics

So just how did a processed meat product come to be associated with unsolicited electronic messages?

The accepted explanation is that it's all the fault of Monty Python's Flying Circus. In one sketch, a group of Vikings chant "SPAM, SPAM, SPAM, SPAM" in a cafe where every meal features the product. The chant drowns out all normal conversation and customers get SPAM whether they want it or not. Sound familiar?

Strictly speaking, spam is more than just email you don't want, such as messages from your bank manager; it's unsolicited bulk email that's sent for marketing purposes. It's characterised by its use of phrases such as "amazing opportunity", "completely legal", "no obligation" and, inevitably, "sex".

Spammers, the people who send spam, collect their victims' addresses in a variety of ways. Lists of email addresses can be bought cheaply and programs constantly crawl the internet, scanning web pages for them.

Some email services are also more prone to spam than others. AOL and Hotmail, for example, in effect give away their subscribers' email addresses, which is why they get more spam than other people.

The science

When you receive a spam email, it may contain a line asking you to reply if you'd like to be removed from the mailing list. Very occasionally, this is a genuine offer; often, it's simply a scam to get you to confirm your email address: usually it has a fake return address that doesn't exist.

This makes replying to spam a pointless activity, but that doesn't mean you should just delete it. All spam should be reported to your ISP to an address along the lines of abuse@yourisp.com - its literature or website should give an address.

Don't just forward the spam, though: some email applications hide a message's sender information, or as it's known, the 'header'.

To get at the full message header in Outlook Express, for example, right-click a message and choose Properties. A window will appear. Click the Details tab and you'll see a long list of text. Copy this text and paste it into the message when you forward it to your ISP.

Unfortunately, headers can be forged and filled with false information. It's difficult to fake everything they contain, though, so ISPs can usually find something useful in there.

Why you need to know about it

All ISPs use anti-spam filters, but spammers are a resourceful bunch and always find a way through. So, make the most of any filter features in your email application.

If you use Outlook Express, for example, you can create filters based on keywords. They detect spam emails and eliminate them from your ISP's server without even downloading them.

You should also use two email addresses: one reserved for friends, family and co-workers, and one for everything else you do online.

If you use a free email service for your 'other' address, such as Hotmail, you can always drop it if it ends up on too many spam lists.

When registering for a website or service, or just shopping online, look for email opt-out options. These are usually hidden away at the bottom of the page. Beware: they may reset themselves if you're sent back to the same page because of an incomplete entry.

JARGON BUSTER

Newsgroups Internet discussion areas where you can post a message and read replies from other people, like on an office noticeboard.

Server A shared, central computer that is linked, directly or indirectly, to computers elsewhere that can access it. Servers are common on office networks for data storage and to provide services such as printing and email. The internet consists of tens of thousands of servers on which web pages are stored.