The weakest link in the protection of a company’s computers against viruses is the individual computer user. There is a strong tendency that the employees assume it is the company’s computer security experts’ job to worry about the viruses and they can bring the problem under control. But everyone must do their share to prevent viruses. Any unsolicited e-mail attachment or any untested type of software may contain a virus. Even the best anti-virus software is not always effective and must be frequently updated. Constant education of all employees about viruses is the key to virus prevention. No one should ever be allowed to relax their defences, even if this means the company must have some rules set that employees might not like.