I agree , but don ' t know with what point of my post you disagree . If you create transactions with a high fee then you block transactions that were created before that from confirming before your transactions confirm , which is exactly what I stated . If you want this to be a prolonged attack you need to sustain this kind of transaction flow . Lets put this way , if the 17000 unconfirmed teansaction were not there , would the transactions fee not be affected ? No , it wouldn ' t , because the fee those transactions pay is so low every client with dynamic fees would pay more anyway . I don ' t even remember last time when 20 satoshisbyte was enough . You also edited out the part about those transactions not requiring high fees that I was essentially replying to .