Microsoft has been working with police in India to shut down fake tech-support centers in the country that are scamming victims in the US and Canada.

On Tuesday and Wednesday, police in the Indian capital of New Delhi raided 16 fake tech-support centers, which were located with the help of Microsoft, according to The New York Times. Three dozen people were arrested in the raids.

The fake tech-support centers swept up in the raids made thousands of dollars by sending out pop-up ads over the internet that claimed users' computers had been infected with a virus. Victims who fell for the scheme would phone the fake Microsoft tech support centers, which would then offer repair services ranging in price from $99 to $1,000.

The raids come a month after Microsoft published a survey that found more than 3 in 5 consumers have encountered the tech-support scams. In addition to pop-up warnings, the fraudsters have been using phone calls, emails, and website redirects to trick users into thinking their computers are infected with a virus or spyware.

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According to Microsoft's survey, 1 in 5 consumers have lost money in tech-support scams. The problem is so widespread that the company said it receives about 11,000 complaints about the scams each month.

The company also told the Times that Microsoft spots about 150,000 pop-up ads related to the scams every day. To fight back, the company has been dedicating resources to help authorities track down fake call centers in India, where the company says many of fake tech support scams are based.

The recent raids are a good reminder to be vigilant around shady pop-ups and other "scareware," which tries to frighten you into thinking your computer has been compromised. One study estimates the tech-support scams have been lucrative enough to extract "tens of million of dollars" in losses from consumers each year. Microsoft has a page with tips on how you can protect yourself.

This article originally appeared on PCMag.com.