You inoculate your computer by running a variety of protective software. There are several kinds:

Antivirus: Antivirus (AV) programs run all the time your computer is running. They monitor what is going on and prevent the activities of viruses, trojans and worms. Because an AV program can only protect your computer against viruses that it knows about and because new viruses are being produced all the time, it is essential to keep your AV software up to date. Most AV programs consist of the main program itself (often called the antivirus engine) and a datafile that tells it how to recognise viruses (which is often called the pattern file). Pattern files are regularly updated and available for download. When you purchase an AV program the cost includes a licence to download updates for a period of time (usually 1 year).

There are any number of antivirus programs, which vary in price, effectiveness and ease of use. A couple of the market leaders provide free copies of their software to non-commercial users. You should only run one antivirus program, since they may interfere with each other’s effectiveness.

Firewall: A firewall is a program or hardware device that prevents hacking. Firewalls can monitor and regulate both incoming and outgoing traffic. If you have a broadband connection to the internet, a firewall is absolutely essential. For home use on a single computer, a software firewall is usually sufficient; if you are running a home network, then it is probably a wise precaution to install a hardware firewall as well. If your home network is connecting through a router then you will probably already have a hardware firewall installed, since most home routers have them built in.

Like antivirus software, there is a range of software firewalls available and, like antivirus, some manufacturers provide free software for home users.

Anti-adware/spyware: There are many programs that will scan your computer to find and remove spyware. None of them seem to be 100% effective; however, you can run several of these programs at the same time. Most anti-spyware programs need to be run manually, although some can be scheduled to run at set times. Some antispyware programs also monitor for incoming spyware and block it.

Spam Filters: There are a number of programs available that will scan your email and attempt to recognize spam. They work in one of two ways:

i) The program scans your mail before it downloads it to your computer, flags the messages that it thinks are spam, giving you the opportunity to delete it before it ever reaches your computer.

ii) The program scans the mail as it arrives and marks anything that it thinks is spam; it may even drop it into a special spam folder. Some e-mail programs include automatic spam filtering.Increasingly, the large internet providers are taking on the task of scanning mail for spam. Some of them provide this service to their members for free, others charge extra for this service.

Windows Updates: The Windows operating system is a hugely complex thing. Many malicious programs, such as viruses, work by exploiting weaknesses that their creators find in Windows. The good people at Microsoft are constantly working to patch these "holes" and to improve their product. From time to time they make the latest improvements available for free download from their website. You should always take advantage of these free updates. You can set your computer to automatically check for, and install, updates.