Apple recently announced new restrictions on the use of cryptocurrencies on iPhones and iPads, a change first noticed by Apple Insider on Monday.

"Apps may not mine for cryptocurrencies unless the processing is performed off device," Apple's app store guidelines for iOS now say. This requirement was absent from the same document just a few weeks ago.

Apple's new policy is apparently motivated in part by concerns that cryptocurrency mining could drain the batteries of mobile devices. "Apps, including any third party advertisements displayed within them, may not run unrelated background processes, such as cryptocurrency mining," the policy states.

Websites have been battling this issue for months: people submitting scammy ads to ad networks that hijack the user's CPU to mine cryptocurrency and send the profits back to the admaker. YouTube was briefly serving up these ads before Google noticed the problem and banned the ads.

But Apple's new policy seems to go beyond obviously abusive cases of surreptitious cryptocurrency mining. The guidelines ban any on-device mining—even if users deliberately download an app whose explicit purpose is to mine for cryptocurrency.

Devices running iOS are not likely to qualify as good mining hardware anyway. Bitcoin cryptocurrency mining has long been dominated by custom ASIC chips. Some other cryptocurrencies are designed to be ASIC-resistant, but even these are predominantly mined on high-end graphics cards with ample processing power and memory. An iPhone or iPad doesn't offer very much raw computing power per dollar, so it probably wouldn't make sense for someone to buy an iPhone or iPad to use as a mining device.

Apple guidelines also now state that cryptocurrency apps "may not offer currency for completing tasks, such as downloading other apps, encouraging other users to download, posting to social networks."

Apple's new policy takes effect at a time of growing concern over scammy behavior in the cryptocurrency world. Google and Facebook both banned cryptocurrency ads from their ad networks earlier this year. And the Securities and Exchange Commission has become increasingly aggressive about shutting down initial coin offerings that are fraudulent or otherwise break the law.