An unidentified spammer wreaked havoc on ZCash node operators by filling transaction blocks with countless shielded transaction outputs that tripled its size to over 100GB. It is estimated that the attack caused the spammer around $10 per day in transaction fees according to the tweet published by Jameson Lopp on October 5th.
Somebody's having fun spamming the zcash blockchain and tripling its size to over 100 GB. Rough estimate is that this attack is costing them ~$10 a day in transaction fees. pic.twitter.com/D8EB1niju3
— Jameson Lopp (@lopp) October 5, 2022
ZCash is a privacy coin that allows users to hide who they are sending money to and how much they are sending, unlike popular blockchains like Bitcoin and Ethereum, where this is impossible.
Since July 2022, attackers have been spamming ZCash as thousands of dust transactions have been submitted daily. As a result, ZCash block space have been rapidly filling up thereby tripling the network’s size to over 100 GB. Despite this, the network continues to function as intended without major hitches.
According to blockchain data, miners on the network verified a block with four shielded transaction Outputs at 1832666 block height. Twitter user Xenu was the first to spot the chain’s size explosion, saying that each block contains a shielded transaction with hundreds of outputs resulting in a chain size increase, maxing each 2MB block every 75 seconds.
The zcash spam attack continues. Almost every block contains a shielded transaction with hundreds of outputs. In doing so, the spammer can successfully blow up the size of the chain by maxing each 2mb block every 75 seconds. The cost of each spammed transaction? Less than a cent.
— xenu (@xenumonero) October 5, 2022
Interestingly, each transaction costs less than one cent, and the attack costs the scammer roughly $10 a day in transaction fees, as stated by Jameson Lopp, the co-founder of Bitcoin security provider Casa.
The motive behind the spam activity is currently unknown, and some have speculated that the attack could have come from a pseudonymous Twitter user named Fiatjat. The suspected attacker previously tweeted that giant organizations should attack Monero and Ethereum to bring down these two networks if they want Bitcoin’s success. Fiatjaf, on the other hand, distanced himself saying the spam was “certainly done by Monero enthusiasts.”
If any giant organization wants to spend money to ensure Bitcoin's success, I believe the best use of your money is now to fund attacks against Ethereum and Monero.
If we can make these two networks crash the Bitcoin ecosystem will instantly get a lot of new useful adepts.
— fiatjaf (@fiatjaf) October 2, 2022
Nick Bax, head of research at Convex Labs, said the spammer was likely targeting ZCash to disrupt its nodes, trick investors into shorting its native token ZEC, or even stop people from running nodes to make eclipse attacks more viable.