A malware attack that turned thousands of websites into cryptocurrency mining engines made just $24, according to the company that develops the software used.

On Sunday, hackers compromised an accessibility plugin, BrowseAloud, which is used to offer screen-reading services on a number of websites including the Information Commissioner’s Office, the Student Loans Company and several English councils.

The hackers inserted a link to a piece of software called Coinhive, which uses the processing power of a website visitor’s device to “mine” cryptocurrencies, draining their batteries or spiking their electricity bill to earn a few pennies a minute. But despite the widespread nature of the attack, which used BrowseAloud as a doorway to more than 5,000 websites, the actual cash earned was minimal.

Speaking to tech site Motherboard, Coinhive said the campaign only mined 0.1 Monero, a privacy-focused cryptocurrency which is currently worth about $245 a coin. That means the entire cryptojacking campaign generated less than $25 – and Coinhive says it hasn’t even paid out that sum to the hackers.

Q&A What is cryptojacking? Show Hide Cryptojacking is the use of a computer to mine cryptocurrency without the permission of machine's owner. A program is loaded on to the unwitting user's machine, typically through the browser when they visit a site with a video or other interactive element, which begins to solve computational problems that generate rewards in the form of cryptocurrency – so called mining. The person, group or organisation that places the program or script on the user's machine then reaps the rewards without compensation for the user. The user's computer slows down when being cryptojacked as the mining operation is computationally intensive, using electricity at an increased rate and often preventing the computer from operating normally.

Cryptojacking has become more common fuelled by the increasing value of various cryptocurrencies. While many applications are malicious, either secretly embedding code such as Coinhive’s software in websites or taking over computers with malware, some organisations have begun to explore the possibility of being open about their intentions.

US news site Salon has begun to incorporate Coinhive in its site in order to monetise those readers who use an adblocker to prevent advertisements from running. In an option labelled “suppress ads”, Salon says users can “block ads by allowing Salon to use your unused computing power”.

In an FAQ posted on its site, Salon says: “We realise that specific technological developments now mean that it is not merely the reader’s eyeballs that have value to our site — it’s also your computer’s ability to make calculations, too. Indeed, your computer itself can help support our ability to pay our editors and journalists.”

The website follows the Pirate Bay, a filesharing website, which began using visitors machines to mine cryptocurrency in September 2017. Although the site was initially secretive about its decision, when users noticed the code running it admitted to carrying out “a test”, and suggested that in the future, such code could replace adverts entirely.