The Swedish tax agency (Skatteverket) took to its website on Friday to warn Swedes about fake emails and text messages.
"These types of messages tend to appear when it is time to refund tax," Lotta Oscarsson, security manager at the agency, told The Local.
For non-Swedish speakers it may be difficult to understand if the message is real or not, but there are signs that can help people see through it.
"We never ask for personal details or bank details via email," Oscarsson continued. "What people need to understand is that these are people pretending to be from Skatteverket."
Anyone who receives a suspicious email should not click on any links, open any attachments, or reply to the message, she added.
The messages often promise tax refunds for a specific amount of money, together with a link promising the refund. Those clicking the link risk getting a computer virus or being infected by Trojan horse malware that can offer hackers access to the victim's computer system.
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Oscarsson added that people who have responded with their bank details should notify the police and contact their bank immediately.
Isabela Vrba/The Local