Snapshot of a fake web page asking users to click all pictures of the straits of the Bosporus. [Photo from web]

One potential buyer joked: "You know nothing when it comes to those pictures". Other netizens said: "Only straight A students could pass this", "I feel illiterate when I just try to buy a train ticket", "Do I have to take an IQ test before buying a train ticket?... Actually I just wanna go home".

Li Tiejun, an engineer who works at Cheetah Mobile Inc, said the picture verification targets ticket scalpers and software that both intend to make a profit from people by purchasing large numbers of tickets and reselling them at a higher price with commission fees.

According to a customer service telephone operator of China Railway, some software can identify simple verification, which they used before, 1,000 times per second. It creates an unfair purchasing environment for other users. "Those pictures are effective since so far the software cannot pass it automatically."

It is reported that the authority has made adjustments to the verification test but no specific changes have yet been announced.