Chinese developers of a controversial software to filter pornography may face legal action from the US makers of a similar Internet filter.

Solid Oak said it had "very solid evidence" to support copyright infringement against developers Jinhui Computer System Engineering Co and Dazheng Human Language Technology Co.

The California-based software maker has sent "cease and desist" letters to Hewlet-Packard and Dell to stop distributing computers containing the alleged copied software and said it was considering seeking an injunction in a US court.