After calling Microsoft a "patent troll" for suing Salesforce.com, Salesforce is suing back.

The San Francisco software company filed a patent suit against Microsoft on Thursday in the U.S. District Court in Delware. The company says Microsoft Windows, Windows Server, SharePoint and .NET platform infringe on five of Salesforce.com's software patents, according to the complaint.

Salesforce has hired lawyer David Boies to handle the case. Boies was the lead attorney for the U.S. Department of Justice during the Microsoft antitrust trial.

Microsoft filed a patent lawsuit against Salesforce in May, claiming Salesforce had infringed nine of Microsoft's patents. To read more about that case, check out our earlier story. Salesforce Chief Executive Marc Benioff responded by calling Microsoft a "patent troll."

The two companies compete in cloud computing and customer-relationship management software for sales departments, also known as CRM software.

The Salesforce patents in the lawsuit are designs for Web-based work sharing, cache management, error reporting and service provisioning.

Salesforce declined to comment beyond the complaint.

Microsoft released a statement from deputy general counsel Horacio Gutierrez saying the company is reviewing the new case. "We remain confident about our position and will continue to press ahead with the complaint we initiated in the U.S. District Court for the Western District of Washington," he said.