Quote from: cousbrdd on November 29, 2015, 08:33:43 PM

Quote from: DannyHamilton on November 29, 2015, 08:31:30 PM

Quote from: basil00 on November 29, 2015, 03:40:05 PM

Another attack...last 6 blocks (edit: and counting) have been hit.

Example: #385910 with 19125 fake sigOps. The block is only 200KB despite a 5MB backlog (according to tradeblock). It seems this attack is very effective.

Edit:
#385911 unaffected (enough high-fee legit txs)
#385912 = 18990 fake sigOps, 280KB.
#385913 = 18945 fake sigOps, 281KB.
#385914 = 17325 fake sigOps, 470KB.
...etc.

There is a DOS attack against the blockchain going on right now. It is causing transactions to take longer than usual to confirm.

In order to pull of the attack the attacker has to pay a higher than average transaction fee. They will eventually run out of money and the attack will stop, but in the meantime you can send your transactions with higher fees to make sure that your transactions get confirmed instead of the attackers (which will force the attacker to spend through their bitcoins even faster to maintain the attack).

This is very interesting... so is this the issue for every transaction at the moment paying 0.0001 ?

Likely so. Like dannyhamilton said, there is a limit of sigops a block can have, if it's more than 20000, nodes will reject it as invalid. The attackers flood the mempool with higher fee, higher sigops transaction. Pools prioritize transactions based on the fees/kb. To pull this attack, the transaction fee must be higher than the average fee. The higher fee paid, the higher priority they have. This attack won't be successful if miners do not prioritize TXes with high sigOPS and fee or miners specifically prioritize some transactions.