In much the same way that organic populations without genetic diversity are vulnerablee to disease, the Internet is vulnerable because the operating systems of over 90 pc of the computers attached to it come from a single vendor: Microsoft. And most users of Microsoft-based PCs use Outlook Express or Outlook as their mail client. A little more diversity would help to slow down the spread of such malicious code. If some Outlook Express users were to switch to Eudora (also available as a free download) and some were to switch to some other client, it could go a long way. It would be even better if some Wintel users were to switch to Mac or Linux.