Google are not going to create an antivirus to protect their competitor's OS Windows. It simply isn't their job, and there are many good companies already offering such a product. Sure, Google has great engineers and data analysts, has money and knows how to get the job done. But it isn't their job to secure a competitor's OS. However, they do many things and vigorously try to protect services and products they offer. Google not only has great engineers, it has great managers/CEOs. They know that building an OS to compete with Windows is going to be very costly, and very risky approach. They might get a positive revenue from this, but they really aren't that hungry for money, they have money. The fact is that 80% they will not be able to outrun Microsoft at their very own game. And they don't feel they need to. Chromebooks are maintained and secured of course. On the other side, you can't say that Microsoft is not investing in security and not doing good things. However their model was different in the not so distant past. They had special partner programs to support 3rd party AV vendors like MAPP and some others. They also had a special page which you could open from the notification about missing AV the first time you started your OS after installation, which lists different AV vendors. You get it?