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There are billions of computers out there running Windows O.S., putting aside the reputation risks, technically, Microsoft could add a backdoor to force users hardware to mine BTC.

Is the combined computer power of those billions of PCs running Windows enough to conduct a 51% attack against bitcoin network?

pee-yay-2021
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  • at first I was thinking about how a botnet could conduct the attack, but then I realize a botnet would just mimic a fraction of the power these companies have. – pee-yay-2021 Dec 28 '22 at 07:50
  • If Microsoft or Google used their software to run unwanted computations on computers globally, how would that be something different than a botnet? – Murch Dec 28 '22 at 19:17
  • no difference at all, what I meant is that originally I was thinking about the idea of any random person attempting the attack, when I realized those companies could just do it right away – pee-yay-2021 Dec 28 '22 at 21:09

2 Answers2

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Microsoft's software runs on a very large number of PCs. However the computers in question generally don't have specialised hashing hardware - they only have typical central processing units (CPUs) that are far far slower at hashing than the ASICs used by miners. A million desktop PCs might have less hashing power than a single ASIC.

See Is the native Bitcoin client intended for mining?

According to Ycharts, the current bitcoin network hashrate is 202.17M TH/s for Dec 27 2022. That is 2 x 102 x 106 x 1012 = 2 x 1020

An Intel® Core™ i7-2600 / 8 / 3.40 GHz has a hashrate of 24 MH/s which is 2.4 x 107

So you probably need to subvert more than 1013 desktop PCs.

Worldometer reports

According to a report by Forrester Research, there were over one billion PCs in use worldwide by the end of 2008, and over 2 billion by the year 2015.

That's only 2 x 109 - If my sums are right, flat out they'd have no chance of making any noticeable impact whatsoever on Bitcoin hashrate.

RedGrittyBrick
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  • I've omitted server-grade CPUs and high-end gaming GPUs to keep the answer simple and because there are probably a lot fewer of these. Even if there were a great many, I'd be surprised if it changed the answer significantly. – RedGrittyBrick Dec 28 '22 at 22:10
  • great answer! I edited (improved) the question based on your input, I guess the initial explanation is no longer required. – pee-yay-2021 Dec 29 '22 at 07:18
  • @pee-yay-2021: Done. – RedGrittyBrick Dec 29 '22 at 10:13
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First they would need to build ASICs to have any hope of competing with the current network hash-rate, secondly it could inspire miners to turn on more ASICs to fight the increased hash-rate, and thirdly the nature of proof of work is such that you cannot guarantee yourself a block no matter how much hash power you really have, there is a huge RNG element involved not to mention networking speed and network uptime. Someone who has been mining their entire life is much more capable of keeping mining up consistently especially on PCs or GPUs than a corporation who is getting into the business just to attack it. There is really a lot going against the possibility.

Poseidon
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  • the question was more like "can all the PCs running Windows around the world surpass the 51% computing power?" (assuming that Microsoft could add a "backdoor" in the O.S. to force your PC to mine btc. in secret, given the fact that there are billions of PCs running Windows) RedGrityBrick gave us the numbers and the answer is surprisingly nope. – pee-yay-2021 Dec 29 '22 at 02:15
  • It's unrealistic to expect them to use their back-doors that way, they do it in sneaky ways. Not to mention they flag all miners as malware. – Poseidon Dec 29 '22 at 02:41
  • that is out of the question – pee-yay-2021 Dec 29 '22 at 07:05
  • – Poseidon Dec 29 '22 at 07:09