"Google is clearly reaching for ways to take more control over the desktop, the Web browser and user content," said Robert Hansen, CEO of security consultancy SecTheory, via instant message. "Native Client appears to be another way to reach into people's computers and use as many resources as possible. It's not a matter of whether it can be done. It's a question of if it should be done. We haven't even solved yesterday's problems yet, let alone another ActiveX clone."

Native Client is not intended to replace any existing technology, Google said. "We believe developers can use this technology alongside others to create applications that provide a richer, more dynamic experience than ever before," the Google spokeswoman said.

The software does not yet work with Microsoft's Internet Explorer, but runs on the Google Chrome, Firefox, Safari and Opera browsers. The developers hope to support Internet Explorer eventually, the spokeswoman said.

To keep Native Client secure, Google has built what it calls an that will analyze code for security bugs and protect the rest of the operating system from being compromised.

"While it's a big challenge to secure Native Client, we believe that the ability to safely run fast native code in a browser has the potential to provide benefits to users and developers," Chen wrote.