They still don’t know where it came from. But when it hit, the Alaskan borough of Matanuska-Susitna was knocked for six. Malware rapidly spread across the borough’s computer networks, disrupting a bewildering array of services. Hundreds of employees found themselves locked out of their work stations. Staff at local libraries received urgent phone calls telling them to quickly turn off all the public PCs. The animal shelter lost access to data on medications required by its furry residents.

It didn’t stop there. An online booking system for swimming lessons went down, leaving people to queue up in person. One borough office had to switch to electronic typewriters temporarily. And Helen Munoz, an 87-year-old woman who has been campaigning for a better sewer system in the area, got an unexpected response to one of her regular calls to local administrators. “Our computers are down,” she was told. She threw her hands up in disgust.

“The cyber-attack, God help us, just about stopped everything, you know,” Munoz says. “In fact, the borough still isn’t squared away with their computers.”

Matanuska-Susitna, known as Mat-Su, is still trying to recover from what happened, months after the attack began in July 2018. When the first signs of malware popped up, no-one expected the turmoil that followed. IT staff initially worked up to 20 hours a day, tasked with digitally scrubbing clean 150 servers.

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Mat-Su, a largely rural borough stretching across an area the size of West Virginia or Latvia, is home to just 100,000 people. It seems a strange target for a cyber-attack.

This is the story of what happened.