The Island's information commissioner's office says the number of people hit by data breaches at the end of last year rose fourfold.
Latest figures from the organisation show between September and December, 12,000 people were affected by breaches - compared to just 2,200 between June and September.
Senior Compliance Officer Laura Doyle says the actual number of breaches in the same period fell from 52 to 39.
She says the rise in people affected is because of hackers targeting large organisations, meaning more people were caught up in individual breaches.
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