I have talked before about some steps you can take to help protect your computer from malware even if you have untrained users like children who are potentially exposing the computer to viruses or other malicious software. In that post, I mentioned teaching them to understand the computer, and helping them to avoid high risk activity which could expose your computer to a virus.
Educating a child about computer safety should be tailored to suit their age. If they are young enough that this is impossible, then I would be quite wary about allowing them computer access. The first step to be taken is to help them understand the potential downsides associated with careless browsing. It can be tempting to simply provide a set of rules and insist that they follow them “because you say so”, but this is generally shortsighted. If you can help to provide them with a deeper understanding, this will allow them to begin to make their own decisions and get them in the habit of taking responsibility for problems.
Explain to them what malware is, what it can do, and how to avoid it. Helping them understand that a virus could do things like steal their parent’s money might help them take the threat seriously. This of course depends on the conscientiousness of the child in question, but is a good place to start. Explaining that it could break or slow the computer can also help.
Teach them about potential vectors for virus infection. For example, help them understand that downloading files or programs from non-trusted sources is a likely avenue for malware infection. Also, begin to teach them critical thinking by explaining phishing scams. Once they are aware of the fact that people will lie to them on the internet and try to convince them to give up their data, they will begin to think more critically about all such requests on them. This is a hugely valuable skill, and not just for internet browsing. Teaching them to take the time to think before acting could save them and you a lot of trouble over time.
Finally, help them understand how to spot a potential infection. There is no way to completely protect any computer which is connected to external sources, so you have to be aware that malware infection could occur. If they understand how to spot it, it might not be a big deal.