BEIJING - Chinese state media on Thursday issued an unprecedented defense of newly required Internet filtering software that must be packaged with every computer sold in China starting next month, after a public outcry at home and abroad.

Although the government says the software is aimed at blocking violence and pornography, users who have tried it say it prevents access to a wide range of topics, from discussions of homosexuality to images of comic book characters such as Garfield the cat.

Chinese authorities rarely feel compelled to justify their tight controls on the world's largest population of Internet users. They are quick to block content challenging the ruling Communist Party's positions on democratic reforms, religious freedom and policies toward Tibet.

Put on the defensive, state broadcaster CCTV announced on its noon news program Thursday that a "vast number of parents and experts" had endorsed the "Green Dam-Youth Escort" filtering software that must be packaged with all computers sold in China from July 1.

The official Communist Party newspaper Guangming Daily ran an almost identical report and praised the software as a breakthrough in the drive for "civilized Internet management and access."

The government has told computer makers the software must either be installed on the hard drive or enclosed on a compact disc. PC makers will be required to tell authorities how many computers they have shipped with the software, which is made by a Chinese developer under contract with the government.

Many industry experts have privately questioned the security of computers and stored information exposed to the software. The Washington-based Computer & Communications Industry Association has said that while blocking pornography is understandable, the technology can easily be expanded into more general censorship.

"The main difference is that it takes censorship down to the level of the individual computer," said Rebecca Mackinnon, a professor at the University of Hong Kong who studies censorship in the Chinese media and online.

That step "very directly affects the individual, and what the individual can do on their computer, how they interface with the Internet," Mackinnon said.

Although porn sites are initially targeted, the program could be used to block other Web sites, including those based on keywords rather than specific Web addresses. Its developer said users could disable blocking of any site or even uninstall the software altogether.

A Ministry of Industry and Information Technology official went on CCTV Wednesday night to deny claims that the software incorporated monitoring or information-gathering functions.

"If there is sexual, violent or other sorts of content unsuitable for young people, then that content will be blocked," said Chen Ying, vice director of the ministry's department of software services industry.

However, the software requirement has prompted widespread derision among China's more than 250 million Internet users, who either accept government controls or have learned to evade them.

Users also mocked a temporary block on networking and image-sharing websites such as Twitter and Flickr last week over the 20th anniversary of the bloody crackdown on Tiananmen Square pro-democracy protests. An earlier attempt to ban foreign video content from Chinese sites fizzled with little fanfare.

The new software's blocking of content about homosexuality prompted a letter of protest from a coalition of Chinese advocacy groups representing gays and AIDS sufferers in the country.

Such content is crucial for psychological and emotional health, and it is "absolutely reasonable and beneficial, as a result, to see the sites accessible over the Internet," the groups said in an open letter e-mailed to journalists.

The move to require the new software "is turning out to be more controversial and unwelcome than decision-makers would like to believe," the official English-language newspaper China Daily said in an editorial Thursday under the headline "Questionable Move."