China is requiring personal computers sold in the country to carry software that blocks online pornography and other Web sites, potentially giving one of the world’s most sophisticated censorship regimes even more control over the Internet.

The software’s developer said Monday the tool would give parents more oversight by preventing computers from accessing sites with pornographic pictures or language. Jinhui Computer System Engineering Co., which won a government contract to develop the “Green Dam-Youth Escort” filtering software, was compiling a database of sites to block.

Although porn sites are initially targeted, the software could be used to block other Web sites, too, including those based on keywords rather than specific Web addresses.