Collaboration company Box.net has raised another $7.1 million from its previous investors, Draper Fisher Jurvetson and US Venture Partners. PEHub first spotted the regulatory filing, and chief executive Aaron Levie confirmed the news to me.

The new money is an addition to the Palo Alto, Calif. company’s second round and brings its total funding to $17.6 million. Levie said:

So as you know, we’re all about the platform, and building a strong platform takes a big engineering investment. And then there are some marketing/sales activities that go around it. But in general, we’re really just expanding our commitment to the platform we’re building.

That platform involves integrating Box’s basic service (which is focused on sharing and managing documents) with a bunch of other online services, most recently Salesforce.com.