Diff Strand Attack

• From this piece by Komodo (16-8-2019):

"A Diff Strand Attack is one where a malicious miner or group of miners who control a large amount of hash power join a small blockchain network, causing that network's hash rate and thus block difficulty to skyrocket. After the difficulty of finding a block becomes extraordinarily high, all of the malicious miners who recently joined the network— causing the increase in hash rate and difficulty in the first place— leave the network just as quickly as they ascended upon it.

The consequence of this sort of attack is that the difficulty of finding a block gets stuck at an extremely high level. When the malicious miners leave the network, they take a vast majority of the network’s hash rate with them. This means that the miners who remain on the network need a very long period of time to find a new block, possibly a few weeks or even a month for one new block. And, since the DAA only readjusts the difficulty level every X blocks, the network still needs to find a number of new blocks before the difficulty is reduced again.

If a blockchain ordinarily produces blocks every 60 seconds, not producing a single block for one full month is akin to the death of that network. Nobody would be able to send or receive transactions. In effect, the blockchain comes to a grinding halt and the coin becomes useless."