This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
...a patch that checks each transaction for payments to certain addresses and refuses to include those transactions in his pool’s blocks. His code refers to it as an “is notorious” check. And
this is fine, he has every right abstain from including those transactions. If he doesn’t include them, the next miner will. But the way it’s implemented is his pool doesn’t just abstain
from including them in blocks, but it deletes them from memory allowing double spends to take their place.
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So a new attack would look like this: Create two transactions; One sending...