Question presented on Reddit: Hi guys, I'm trying to understand why Xtrabytes isn't vulnerable to a 51% attack? Is the consensus driven by the majority of static nodes? Without a proof of work, what's stopping someone setting up a majority of Static Nodes? Answer: How can the 51% attack even be possible? We really need to stop comparing PoSign to what you already know about crypto. XTRABYTES is changing the game in just about every way that is necessary. The truth of the matter is that BLOCKCHAIN can be better! There is a reason why setting up a STATIC node has a price and that price is in the form of a deposit (yes you get it back later if you break your node) and that deposit is the basis of trust. So, if we travel down this road the writer suggests, the person wanting to own 51% of the nodes would have to have purchased 51% of the STATIC supply of XBY. This is not technically or financially impossible, so you can have that. But, here is where the idea falls flat; just because you own all this XBY does not mean you have all the STATICS. The next thing you might try is to convince all the owners to sell their STATIC registrations to you. Well, I am sure many will happily sell to you for a premium and your investment will become quite extensive. However, you will run into brick walls because there are many who simply will NOT sell and I am one of them. STATIC ownership is like owning real estate in the XTRABYTES universe. These little pieces of property even offer income producing asset status in the future because as we begin to support DApps and Modules, such as: X-CHANGE, X-VAULT and others which will offer “profit sharing type arrangements” you will find it very difficult to get people to part with their daily income asset stream. But, let’s entertain this a bit more: Assume a large “Google type corporation” decides they want to take over XTRABYTES and they go out and start targeting all the STATIC owners and they manage to convince 51% of them to bow out, to the tune of a couple Billion dollars. Now what? Are they going to flush the project down the drain along with their money? Not likely... Otherwise, here is the part you must understand: The other 49% are part of the original XTRABYTES and there could be 1 single HOLDOUT that is an offline STATIC (call it an ace in the hole) that in the event of an attack where someone tries to gain control of the network can be activated to come back online and it could blacklist the 2 Billion Dollar STATIC network that has been bought by a rogue corporation that had bad intentions for the XTRABYTES network. It would now be up to the owners of the blacklisted STATIC nodes to come back into consensus before they will be allowed to return to active status. So, to answer your question is a more simple way: 51% attack does not exist as a possibility with the XTRABYTES network. This is just one of MANY flaws in the Bitcoin system that is being corrected by the XTRABYTES system.