Information security experts are worried that Yahoo's massive password breach may result in usage of the data to open locks up and down the web. While its unknown to what extent the stolen data has been or will be circulating, giant breaches can send ripples of insecurity across the internet.

Data breaches on the scale of Yahoo are the security equivalent of ecological disasters, said Matt Blaze, a security researcher who directs the Distributed Systems Lab at the University of Pennsylvania, in a message posted to Twitter.

A big worry is a cybercriminal technique known as 'credential stuffing', which works by throwing leaked username and password combinations at a series of websites in an effort to break in, a bit like a thief finding a ring of keys in an apartment lobby and trying them, one after the other, in every door in the building. Software makes the trial-and-error process practically instantaneous.

The first hint that something was wrong at Yahoo came when Motherboard journalist Joseph Cox started receiving supposed samples of credentials hacked from the company in early July.

Several weeks later, a cybercriminal using the handle 'Peace' came forward with 5,000 samples and the startling claim to be selling 200 million more, the Associated Press reported.