Ransomware infections on computers have skyrocketed in recent years, but that doesn't mean the criminals have forgotten about your smartphone.

Kaspersky Lab released a report on Wednesday demonstrating a four-fold increase in ransomware attacks hitting Android mobile users in just a year, which it called a "worrying trend."

"The extortion model is here to stay," Roman Unuchek, mobile security expert at Kaspersky Lab, said in a statement.

"Mobile ransomware emerged as a follow-up to PC ransomware and it is likely that it will be followed-up with malware targeting devices that are very different to a PC or a smartphone."

In the typical ransomware on PCs, a user's system is infected and all its files are encrypted. The attacker then displays a message telling them they have a few days to send money or their files will be destroyed. It's a little different on mobile — much of the malware can't encrypt other files — but the display of popup messages or the locking of the screen will still ask for money.

The ask is usually around $100 to $200, according to Kaspersky, which notes that the upward trend in usage is no doubt because users tend to pay.

Ransomware can affect iOS devices, but they are not as susceptible as Android. For now, Kaspersky advises users to be careful with what they download onto their device, conduct regular data backups, and if infected, don't pay.

"Every bitcoin transferred to the hands of criminals builds their confidence in the profitability of this kind of cybercrime," the lab wrote.