In the non-digital world, you have a lifetime’s experience of what is risky. Walk near the edge of a cliff or down a dark alley at night and you instinctively know there's danger. Online, it’s different. You need to know what is out there before you can be wary of it.

Viruses

Viruses are small, malicious computer programs that try to infect computers, spreading from one machine to the next.

They spread in different ways:

• As attachments to emails. An infected computer can send out tens of thousands of emails, each carrying the virus. Often it will use your email address book to find new people to attack.
• By pretending to be something they’re not (a ‘trojan’). For example, a file that looks like it contains a picture of a celebrity.
• As downloads on malicious websites. In some cases, just visiting the site can download the virus. In other cases, they can be hidden inside seemingly-innocent programs that you download from the net.
• Hidden inside documents (‘macro viruses’)
• Directly over the internet from one computer to another (a ‘worm’). Once infected, a computer will scan the internet looking for computers that are vulnerable to attack and send them a copy of itself.

Because they use different techniques to spread, you need different defences for complete protection: anti-virus software, a firewall and a bit of commonsense.

These viruses, trojans and worms are often collectively called ‘malware’ but on this site we use the more familiar term ‘viruses’ to mean all three.

Besides replicating themselves, like a missile, viruses also carry a dangerous payload. This is the mission that their original author sent them out to do, for example:

• Sending out spam email.
• Opening a back door onto your computer to give criminals control.
• Scanning your computer for personal information such as passwords.
• Displaying unwanted advertising.
• Hijacking your web browser.
• Switching off your security defences.
• Hosting phishing websites to con other users.
• Launching denial of service attacks on other websites.

Much of this can happen on an infected computer without you even knowing about it.

Threats to your privacy

The internet makes it easy for online criminals to attack your privacy:

Spyware

Spyware doesn’t try to replicate itself like a virus. Instead, it relies on people downloading it mistakenly, often alongside other programs such as peer-to-peer music sharing programs.

It causes a range of problems, including:

• Annoying pop-up adverts.
• Taking over your web browser.
• Scanning your computer for private information like credit card numbers.
• Slowing down your computer and internet connection.
• Downloading viruses.
• Being very difficult to remove.

Wi-Fi eavesdropping

If you use a wireless, or Wi-Fi, network you’ll know that it lets you connect to your broadband internet connection using a radio link with a range of several hundred feet. However, this flexibility has a downside.

Without security, other people can also connect to your internet link if they are within range. This means you could be paying for your neighbour’s internet use! 

A more sinister risk is that people can, with the right equipment, eavesdrop on you and gain access to your computer over the wireless link.

Hacking

Thanks to automated tools, viruses and spyware, the job of breaking into someone’s computer is not the demanding, high-tech task depicted in the movies.

Hackers are increasingly motivated by money and stealing your bank account and credit card information could make it well worth a criminal’s time to attack you.

While everyone is at risk, small businesses and charities are being singled out for hacking attacks because they have databases of personal information that can be used for identity theft on a grand scale.

Physical theft

Tens of thousands of laptops are stolen in the UK every year. If a criminal has your laptop, they have access to all the data on its hard drive. The same applies to computers stolen from the home or pocket computers and mobile phones.

Threats to your wealth

Fraud

Fraud is a growing problem online. Conmen are the dot.com entrepreneurs of crime. Common tricks include:

• Phishing, which means using a fake bank or credit card website and persuading you to enter private information that can be used to steal from you.
• Advance fee fraud. Typical examples include paying an administration fee to collect a non-existent lottery prize or sending money to help secure a share of an African dictator’s Swiss bank account.

Identity theft

Identity theft is exactly as sinister as it sounds. Criminals use a combination of social engineering (basically con tricks), evil hacker tactics like viruses and real world information such as credit card statements picked out of your rubbish bin to impersonate you. With this information they can, for example:

• Empty your bank account.
• Max out your credit cards buying stuff for themselves.
• Buy cars on tick, in your name.
• Impersonate you online, for example using your identity in online auctions or e-commerce site.

Spam email

Increasingly, spam is changing from a minor nuisance to a major problem. More than half of all the email on the internet is unwanted junk mail, which means you’re paying for the spammers’ bandwidth.

Because spammers earn money if you buy their wares, whether it is herbal Viagra, porn or online gambling, they have every reason to be persuasive and persistent.

Threats to your family

Material that is normally on the top shelf in a newsagent (or worse) is only a click away. In some cases it is being sent to people via email, whether they want it or not. Without proper protection, your family could be exposed to hard core pornography or violent images.

Anyone can email anyone else and there’s no guarantee that people are who they say they are. The same is true for instant messaging. If you and your family are not on guard, the risks are obvious and alarming.