As the BBC News Online opinion poll shows, many people worry about becoming victims of cyber-criminals. More than a third of people questioned by ICM said the risk of computer crime put them off using online banking and shopping services. It is a fear that may jeopardise the future growth of e-commerce.
As a result of the widespread use of e-mail, there is the possibility of your computer being trashed by a virus attack. For organisations that depend on computer networks - and that includes virtually all major companies - the threat can take many forms, depending on the motives of the person trying to penetrate your system.
So who is doing what? The following categories of cybercrime have been identified by Britain's National Criminal Intelligence Service and other law enforcement agencies.
Recreational Hackers: These hackers may appear relatively benign. Many are attracted by the challenge of gaining access to a system and showing up failings in the company's security. But they can still cause damage that results in a financial loss for their victims.
Criminal-minded hackers: Their motives may include financial gain, sabotage or revenge. In 1994, the US Citibank was robbed of $400,000 by Russian cyber-criminals. One hacker was arrested and jailed for three years and according to the bank it recovered most of the money. Robbing banks is difficult, because of the security systems that are usually in place and vast majority of such crimes are committed only with the help of someone who works for the bank or organisation being targeted. The theft of confidential information from companies may also be used for blackmail. Hackers can also carry out espionage and sabotage. A disgruntled employee may attempt to vandalise a computer system.
Political Hackers: Political activists - sometimes called "hacktivists" - have defaced web sites in an attempt to put across their message and discredit their opponents. In 1998, hackers altered hundreds of web sites around the world to include an anti-nuclear message.
Denial of Service Attacks: Another tactic is the "denial of service" attack. A web site is flooded with data with the intention of making it crash, and preventing legitimate users from gaining access. It can take hours for the company to regain control, by which time it may have suffered considerable financial losses. The FBI says the level of such attacks is "unprecedented".
Insiders: While attempts to hack into computers from the outside have attracted the most attention, there is evidence that many such attacks are the work of insiders, employees who bear a grudge or simply see an opportunity to make money. In 1998, the Department of Trade and Industry estimated that over a six-year period, internal hacking had cost UK organisations £1.5bn.
Viruses: Two hundred new computer viruses are identified each month. These malicious programmes were once spread by floppy disk, but the growth of the internet has increased the potential for damage. The virus is either hidden inside a file, downloaded from the Net, or attached to an e-mail message. Despite the increasing use of anti-virus software, programmes like "Melissa" (1999) can still infect tens of thousands of computers.
Piracy: Software piracy means a loss of potential revenue to the companies that manufacture games and programmes for business users. Programmes can be downloaded from the Internet and copied onto CD-ROMs. The MP3 format has made it possible to distribute digital music files via the internet. Musicians complain that it deprives them of royalties.
Fraud: Financial scams and get-rich-quick schemes have been given a new lease of life on the internet. For example, the share price of a company can be inflated by false rumours of a takeover. Online auction sites also offer opportunities for fraud, with money pocketed and goods not delivered. A credible looking website that provides no way of checking that the site owner is legitimate may also conceal an internet scam.
Gambling: Virtual casinos operate in cyberspace, many based in countries that put them beyond any regulation. There's concern that organised crime may take advantage of such operations to launder money.
Pornography & Paedophilia: Paedophiles use the internet to exchange pornographic images of children. Hundreds of thousands of obscene images have been seized as a result of investigations by police forces in many countries. Paedophiles use newsgroups and chat rooms as meeting places.
Cyber-stalking: Unwanted e-mail from a persistent sender can amount to harassment, and if the culprit manages to conceal his identity, he may be difficult to catch. Stalkers may try to obtain personal information about their victims online.
Hate Sites: Websites run by extremists are used to promote racial hatred. Publishing someone's name and address on the internet may constitute a threat to their safety. In the US, an anti-abortion web site was sued after inciting people to target pro-choice doctors and putting congratulatory comments next to the names of pro-choice doctors and lawyers who had been attacked or killed.
Criminal Communications: NCIS believes that a number of criminal groups active in the UK and Europe are using the internet to organise their criminal activities. They are believed to include drug importers, software counterfeiters, football hooligans, and far-right activists. E-mail is their means of communication. Paedophiles use encryption as a way of keeping their activities private.
So faced with this variety of threats, what should the rest of us - individuals and companies - be doing to protect ourselves against the threat of becoming cyber-victims? A police officer who deals with computer-related crime said his advice was simple: "Get anti-virus software, and make sure you update it frequently. And think seriously about firewalls."
The US Federal Trade Commission has drawn up a list of the "Top Ten Dot Cons" which aims to help consumers avoid the traps waiting for the unwary surfer. The agency also logs complaints and enters them into a secure, online database - Consumer Sentinel - available to law enforcement agencies worldwide.
One of the tips offered seems fairly obvious, but clearly needs repeating in view of the number of people who have been caught out by unscrupulous internet traders. Be wary of any company operating online that does not clearly state its name, address and telephone number.