The world’s biggest social networking website, Facebook, is acting as if it “owns the internet” according to the founder of a Chicago educational startup, Teachbook, which is the latest target in a campaign by the Silicon Valley empire to prevent outsiders from cashing in on its success.

With just two employees and a few dozen registered users, Teachbook is intended as a “productivity suite” allowing educational professionals to share lesson plans, homework assignments and coursework. It barely registers in the online universe — but it has attracted a federal court lawsuit from the empire founded by Mark Zuckerberg, which argues that the suffix “book” should be its exclusive domain.

A complaint filed by Facebook in California accuses Teachbook of “riding on the coat-tails of the fame and enormous goodwill of the Facebook trademark” and demands that it change its name.

“They seem to think they own the internet and the word ‘book’,” said Teachbook’s founder, Greg Shrader. “We think they’re wrong on the merits of the case.

“How can this tiny little company in Northfield, Illinois be a threat to a multibillion-dollar social networking site?” The altercation, which Shrader views as the heavy-handed behaviour of a multinational, is the latest aggressive effort by Facebook to protect its reputation. The company, valued at an estimated $33bn, has already forced other sites, including a travel startup called Placebook, to change their names.

Facebook recently mounted a rebuttal against a soon-to-be-released Hollywood film, The Social Network, that depicts it as a product of a series of betrayals among university friends. Facebook has described the movie, which stars Jesse Eisenberg as a party-loving Zuckerberg, as “fiction”.

Experts say Facebook’s efforts to protect the word “book” would face an uphill battle if they ever came to trial — but smaller rivals are unlikely to battle that far. Tania Clark, trademark partner at the intellectual property law firm Withers & Rogers, said: “I believe it will have difficulty enforcing this trademark here, yet 90 per cent of cases like this never make it to the courts as the smaller company caves in.”

In a statement, Facebook said it would not tolerate outsiders cashing in on its brand. A spokesman said Facebook had no dispute with alternative uses of the word “book” and had never objected to many other websites, such as the used car site Kelly Blue Book.

“However, there is already a well-known online network of people with ‘book’ in its name,” said Facebook’s spokesman. “Of course the Teachbook folks are free to create an online network for teachers or whomever they like, and we wish them well in that endeavour. What they are not free to do is trade on our name or dilute our brand while doing so.”