To protect its cloud, Microsoft bans crypto mining from its online services

Updated Microsoft has quietly banned cryptocurrency mining from its online services, and says it did so to protect all customers of its clouds.

The Windows and Azure titan slipped the prohibition into an update of its Universal License Terms for Online Services that came into effect on December 1. That document covers any "Microsoft-hosted service to which Customer subscribes under a Microsoft volume licensing agreement," and on The Register's reading, mostly concerns itself with Azure.

Microsoft's Summary of Changes to the license states: "Updated Acceptable Use Policy to clarify that mining cryptocurrency is prohibited without prior Microsoft approval."

Within the license itself there's hardly any more info.

A section headed "Acceptable Use Policy" states: "Neither Customer, nor those that access an Online Service through Customer, may use an Online Service: to mine cryptocurrency without Microsoft's prior written approval."

Microsoft appears not to have publicized this decision beyond the Summary of Changes page and, in recent hours, in an advisory to partners titled: "Important actions partners need to take to secure the partner ecosystem."

That document states "the Acceptable Use Policy has been updated to explicitly prohibit mining for cryptocurrencies across all Microsoft Online Services unless written pre-approval is granted by Microsoft," and adds: "We suggest seeking written pre-approval from Microsoft before using Microsoft Online Services for mining cryptocurrencies, regardless of the term of a subscription."

Microsoft told The Register it made the change because "crypto currency mining can cause disruption or even impairment to Online Services and its users and can often be linked to cyber fraud and abuse attacks such as unauthorized access to and use of customer resources.

"We made this change to further protect our customers and mitigate the risk of disrupting or impairing services in the Microsoft Cloud."

Permission to mine crypto "may be considered for Testing and Research for security detections."

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Microsoft is not alone in banning crypto mining without permission. Google Cloud forbids it without written approval (see clause 3.3). Oracle [PDF, see clause 1.3] and OVH don't allow it. Digital Ocean also requires written permission.

Amazon Web Services does not allow it in its free tier. Microsoft has done likewise for some time, and barred student accounts from mining activities.

But there hasn't been such a blanket proscription before. So why now?

Microsoft rushed us the statement above, and before we received it we speculated that Microsoft might be worried that miners would not pay their cloud bills.

With the crypto sector beset by scandal and the values of many tokens well below historical highs, miners' positions may be … let's say precarious. That Microsoft has reminded partners not to allow crypto mining supported this hypothesis because Microsoft does not deal directly with most customers. If anyone knows Azure-using crypto miners, it's the partners who signed them up.

The Register also often hears whispers of Azure capacity shortages. Maybe Microsoft is trying to slough off the crypto sector and find more stable customers for the infrastructure it has spare?

Our theory on the need for permission to mine – Microsoft would not allow computationally expensive proof of work techniques but might allow the less demanding proof of stake method – proved to be mere speculation if the company's explanation was comprehensive. ®

Update at 0515 UTC, December 15

This story was revised to include Microsoft's explanation of its tweaked policy.