In message , nightjar writes
It's largely a matter of attitude and policy. Microsoft has tried for years to move software out of computers and into its own servers, so you would download Word when you needed it and be charged by the hour. This gets them away from the enormous problem of maintaining a revenue stream by constantly producing new versions of everything. Secondly, Microsoft is trying to make money from third-party content, i.e. entertainment, again as a continuous source of revenue. Both ambitions cause Microsoft to look favourably on downloading and running just about anything from anybody on the Internet, and to downplay the risks, even to themselves.
Hence an email program which routinely runs attachments received in emails. For a long time, it was not possible to stop Outlook/Outlook Express running attachments automatically. The preview pane meant that it was not even necessary to explicitly look at an email. This behaviour went on long after it became glaringly obvious that it was a stupid idea. The question is, why was it *ever* considered anything other than a stupid idea? Even after it had been 'stopped', it was possible to include an executable in an email and tell Outlook that it was a harmless audio file. Outlook would swallow this and pass it to Windows. Windows would assume Outlook knew what it was doing, and run the file. I kid you not.
Linux descends from Unix, which came into being as a network operating system. Network administrators were basically there to stop users ('lusers') doing stupid things, and Unix was designed with that purpose strongly in mind. Microsoft needs to regularly sell new software with new bells and whistles, *to schedule, not when it's ready*, and its job is done once the computer manufacturer has pre-installed Windows. Neither offers any warranty, but which approach would you objectively expect to result in better security?
Remember with viruses, it's not just the number of infections that matter, it's the rate of spread. If the common cold was likely to infect less than one other person during the course of the disease, it would not simply be extinct, it would never have evolved. Linux viruses exist, bugs in Linux program exist, but if an infected installation is unlikely to manage to infect another, the infection doesn't spread. There are still machines infected with the Swen virus (though Demon finally seems to have figured out how to spot the emails), but it will never again spread because most machines are now immune.
It's not *just* the variation in Linux installations, not *just* that few people run as root, not *just* that nobody has yet been stupid enough to write a mail client like Outlook. Each of these things keeps the loop gain well below unity, and it would take major changes in all of them to make Linux viruses a problem. Immunity to such viruses simply requires the user to get one of them right.