BEIJING — Chinese Internet censorship is getting more sophisticated and systematic, which has grim consequences for freedom of expression and media rights, according to a new report by an anonymous IT expert with knowledge of the system’s inner workings.

The Internet is booming in China — the country has 162 million Internet users and at least 1.3 million websites — but free expression is closely watched by surveillance experts and material is scanned for political content, often with the help of big international service providers such as Yahoo! and Google.

“This system of censorship is unparalleled anywhere in the world and is an insult to the spirit of online freedom,” the human rights groups which issued the report, Reporters Without Borders and Chinese Human Rights Defenders, said in a joint statement.

The report details how the Communist Party, which is holding a major five-year congress next week, has deployed colossal human and financial resources to obstruct online free expression.

There are daily instructions to online web editors about what stories can and cannot be run, and 400-500 sensitive or taboo words are banned. Websites self-censor these words to avoid fines, it said.