By Owen Fletcher
June 8, 2009 04:14 AM ET

China will require Web-filtering software on all computers sold in the country, another step in its efforts to control pornography and other content on the Internet. The move follows a government crackdown on online smut that has led to the closure of thousands of Web sites this year, and concern that such campaigns could expand to target content that is political rather than pornographic.

PC makers will be required to pre-install the Web site-blocking program or offer it on a CD-ROM included with all PCs sold in China after July 1, according to a translation of a Ministry of Industry and Information Technology notification seen by IDG News Service. The move is meant to protect youth from "unhealthy" information online, according to the statement.

The program, called Green Dam Youth Escort in Chinese, blocks only sites with pornographic content, and parents can turn it off, said Bryan Zhang, general manager of Jinhui Computer System Engineering, which designed the software. But the measure triggered concern about wider censorship. China blocked access to Web sites including Microsoft's Bing search engine last week, adding to a list of previously banned sites including YouTube and some blog services.

Twitter and Hotmail were also blocked ahead of the 20th anniversary last week of Beijing's bloody crackdown on democracy protests, though those Web sites could load again today. Dell Inc. will consider including the software with new PCs only if its purpose is to block pornographic content from children, and only if it can be disabled, said Amit Midha, Dell's president for Greater China.