Chinese Internet hosting services, including wireless and IM services, are filtering communication through key word blocking mechanisms.

Chinese internet laws and the internet police force never made the forbidden words explicit. But some Chinese hackers located a document within the installation package of QQ instant messaging software. The file contains over one thousand words which will be blocked by the service.

QQ is China’s most popular IM service. Because of its high traffic volume, it is technically hard to build in the key word filtering mechanism on the server’s end. Instead, Tencent, which owns QQ, sneaked in a filtering program file in their installation package at the client end.

When a client installs the software on his/her own computer, a program file is automatically included. This way, all the forbidden keywords will be automatically blocked when the client runs QQ.

Recently, some Chinese hackers published the file on the Internet. The censored key words list is commonly used not just for QQ, but also for all websites, BBS and text messaging services. One Internet user did a rough breakdown of the list: About 15% of the words are sex related, the rest are all related to politics.

For a list and more details, read China Digital News.