Starbucks has acknowledged that visitors to one of its branches were unwittingly recruited into a cryptocurrency mining operation, the BBC reported.
The wi-fi service provided by one of the coffee chain's Buenos Aires outlets surreptitiously hijacked connected computers to use their processing power to create digital cash.
It is not clear how long the malware involved was active or how many customers were affected.
The issue was identified only when Noah Dinkin, the chief executive of a New York-based technology company, logged into the service and noticed the problem.
Hi @Starbucks @StarbucksAr did you know that your in-store wifi provider in Buenos Aires forces a 10 second delay when you first connect to the wifi so it can mine bitcoin using a customer's laptop? Feels a little off-brand.. cc @GMFlickinger pic.twitter.com/VkVVdSfUtT— Noah Dinkin (@imnoah) December 2, 2017
"As soon as we were alerted of the situation in this specific store last week, we took swift action to ensure our internet provider resolved the issue and made the changes needed in order to ensure our customers could use wi-fi in our store safely," Starbucks replied to Mr Dinkin's tweet, after investigating the issue.
The company later told the Motherboard news website that the wi-fi service was not something it owned or controlled directly itself.