Coindesk recently published a blog which “attacks the idea that true immutability can be achieved in blockchain systems, arguing a more relative definition of this feature better encapsulates what’s the technology can achieve.” The May 9, 2017 article entitled “The Blockchain Immutability Myth” was a blog from “Dr.  Gideon Greenspan is the founder and CEO of Coin Sciences, the company behind the MultiChain platform for private blockchains.” Dr. Greenspan cited this example about private blockchain immutability and vulnerability if participants in the chain jointly undermine security:

Let’s imagine a private blockchain used by six hospitals to aggregate data on infections. A program in one hospital writes a large and erroneous data set to the chain, which is a source of inconvenience for the other participants. A few phone calls later, the IT departments of all the hospitals agree to ‘rewind’ their nodes back one hour, delete the problematic data, and then allow the chain to continue as if nothing happened.

Dr. Greenspan’s blog should help the dialogue about blockchain security!