Spammer in the works

The internet has provided a new outlet for the mischievous urges of youths who a generation or two ago were indulging in annoying but essentially harmless pranks in the real world. These days, many of those pranks have been transferred to cyberspace. Computer viruses are one form of modern mischief. Another is the hacker's art of defacing websites.

Both can be relatively harmless, if annoying. A virus that merely causes your PC to display a cheeky message on a particular date, for example, isn't particularly damaging. Similarly, an "I wuz here" message left behind by a hacker on a website whose security they have compromised might actually be doing the site owner a favour if it alerts them to a security problem without causing further damage.

But extreme forms of each activity can do real harm, counted in billions of dollars of lost productivity, as organisations are forced to shut down their computer systems and purge them of infections. After a number of cases of worldwide chaos caused by viruses, anti-virus software makers, internet service providers (ISPs) and computer users have become much more vigilant about warding off infection.

The scale of the virus problem is enormous. Neil McCallum, security product manager at the country's largest ISP, Telecom-owned Xtra, says since Xtra began filtering for viruses in the middle of 2002, it has intercepted 200 million of them. And according to anti-virus software maker Trend Micro, the ones that slipped through cost organisations US$55 billion in 2003 alone. The expense comes from interruption of normal business as networks are shut down and viruses laboriously removed from thousands of PCs.

McCallum says two levels of protection are essential to keep viruses at bay: the first line of defence is ISP filtering and the second is PC anti-virus software.

"The thing about anti-virus efforts is that they're reactive," says McCallum. "There's always a response time between a brand new virus coming out and our ability to detect it."

Organisations like Xtra are locked in a war with virus writers, McCallum says, with the perpetrators constantly working on virus variants designed to get around detection systems.

"Desktop protection is important, because if something does slip through in that first hour while the boffins are trying to work out how to identify a new virus, anti-virus software on your PC gives you the opportunity during a system scan to clean that up."

Aside from viruses, Xtra also filters out another bothersome form of email, spam. Spam messages typically advertise a product or service that is available online. They are sent in their millions to vast databases of email addresses that can be bought on CD. The addresses are collected by a combination of legitimate and nefarious means - perhaps from websites or internet newsgroups or innocently provided when signing up online for some service or other.

The products spammers push are frequently bogus and usually give themselves away by sounding too good to be true. That doesn't stop plenty of people falling for them, however.

McCallum says spam is being filtered by Xtra at a rate of about 60 million messages a month; it is thought to account for about half of all email traffic.

A recipient of a spam message should delete it without responding, since doing so alerts the sender to a live email address. Spam is often also a way of transmitting viruses.

McCallum says being cautious is a good habit to cultivate in any online transaction, even with filtering systems in place. Opening email file attachments, for example, is a prime cause of virus infections; attachments should only be opened if they come from a trusted source and their contents are known.

Trust is even more important when it comes to paying for goods and services online. Carrying out an online transaction that involves communicating through a secure server gives a certain level of comfort - all information passed between you and the server is encrypted - but the greatest guarantee of security is in trusting the organisation you're dealing with.