BEIJING -- Web-filtering software that the Chinese government will require on all new personal computers includes data files containing political keywords and Web addresses, suggesting it could block more than just pornography, say people who have studied the program.

A notice sent to PC makers last month said they must include the software with all new PCs shipped in China as of July 1. Chinese officials and the main developer of the software have said the purpose of the software, called Green Dam-Youth Escort, is to enable...