Security researchers at Avast have highlighted three 'VPNs' on Apple's App Store that, number one, don't work and, number two, try to trick customers out of their money through excessively costly subscriptions. The apps charge $9.99 per week - instead of per month, which would be more normal.

Avast calls the apps "fleeceware" because they behave overcharge users but do not contain any directly malicious code, reports AppleInsider. Since the actual VPN service they offer doesn't work, they can't spy on users either.

"Fleeceware apps fall into a grey area," writes Nikolaos Chrysaidos, head of mobile threats and security at Avast, "because they are not malicious per se. They simply charge users absurd amounts of money."

The three apps are Buckler VPN, Hat VPN and Beetle VPN. We won't link to them for obvious reasons, but at least two are still on the App Store at time of writing (we couldn't find Hat VPN). Buckler and Beetle are rated at 4.7 and 4.6 stars respectively, which Avast says is likely the result of fake reviews.

Since you send all internet traffic over a VPN, it's vital that you stick to reputable services. Our current recommendation is NordVPN, but visit our guide to the best VPNs for iPhone for detailed advice.

This article originally appeared on MacWorld Sweden. Translation by David Price.