Apple recently removed a Monero-mining app from its Mac App Store called Calendar 2. The app allowed users to chose to allow it to mine Monero in the background, a move which Apple says put a burden on user’s devices. Before being pulled, the app raked in $2,000 in only three days.

Developed by Qbix, Calendar 2 was essentially an improved version of Apple’s Calendar app. It allowed users to access premium features by either paying an $18 full-app purchase, or a $1 monthly subscription. Alternatively, Calendar 2 gave them the chance to donate some of their CPU resources to mine the privacy-centric cryptocurrency.

However, the app’s mining feature had issues. According to a Twitter user, it ate significantly more CPU power than the supposed 10-20 percent the app claimed it did, and it wasn’t possible to opt out.

@SGgrc @QbixApps Calendar 2 for Mac (from the App Store) launched a cryptocurrency miner without my permission. Then it ate 200% CPU until I found it and killed it. I didn't expect a miner infection from an App Store vendor. Wow. It runs the xmr-stak Monero miner. — Fred Laxton (@fredonline) March 12, 2018

After it started mining Monero, 9to5Mac claims Apple pulled the app for violating its guideline 2.4.2. The guideline reads “design your app to use power efficiently. Apps should not rapidly drain battery, generate heat, or put unnecessary strain on device resources.”

In an emailed statement to Ars Technica, Qbix CEO Greg Magarshak revealed the company that provided Calendar 2’s mining code would take a long time to work out the cause of the CPU issue. As such, it removed the Monero-mining feature.

While the company could have benefitted from the cryptocurrency miner’s income, the statement says, it chose to pull the feature and get it back on the app store. Apple reportedly worked with Qbix to remove the feature in a timely manner.

Leaving the mining business

Magarshak further revealed he is worried about the “growing global energy use of Proof of Work based crypto.” Per his words, these cryptocurrencies give miners “a dangerous set of incentives which can lead to electricity waste on a global scale we’ve never seen before.”

Magarshak’s email further claims the incident saw Qbix give up on the mining business. He wrote:

“Ultimately, even though we technically could have remedied the situation and continued on benefiting from the pretty large income such a miner generates, we took the above as a sign that we should get out of the “mining business” before we get sucked into the Proof of Work morass of incentives.”

His solution, was to launch a company called Intercoin Inc. The company reportedly aims to solve some of the issues proof-of-work based cryptocurrencies bring up. He stated:

“I believe in the future of crypto currency, just not Proof of Work. So we started a spinoff company, Intercoin Inc. to make a global currency and payment network that doesn’t rely on Proof of Work, Proof of Stake and can handle an unlimited number of transactions at the same time.”

While Calendar 2 gave users a choice between mining and paying, hackers usually don’t. As covered by Ethereum World News the cryptojacking trend even saw hackers use Telsa’s cloud to mine cryptocurrencies. Hackers are now even stuffing Monero ransom notes inside DDoS attacks.