Port80 Software, a Microsoft partner, has released a new survey showing that the Microsoft Internet Information Services 6 Web server has overtaken the Apache open-source Web server among Fortune 1000 Web sites.

In the survey released on Oct. 11, Port80 Software said IIS 6 more than doubled its market share over the last year, to 27 percent. However, IIS 5 remains the most popular Web server among Fortune 1000 users, according to the survey.