Sweeper bots burn $4,800 in Bitcoin fees chasing $12.67

The target was a SegWit address whose private key was effectively public, as it used the coinbase transaction ID from Bitcoin block 924,982 as the key. This made the key derivable by anyone running the right script, allowing any coins sent to the address to be claimed by whoever moved first.

Two small deposits arrived at the address - 0.00018209 BTC and 0.00002096 BTC, totaling 0.00020305 BTC. Both were swept within minutes of being sent, leaving the address with a zero balance and no remaining unspent outputs (UTXOs).

Fee War

The expensive part was the competition. Several bots spotted the deposits simultaneously, each trying to claim them using replace-by-fee (RBF), a Bitcoin feature that allows senders to swap unconfirmed transactions for higher-fee versions. Fee rates hit 12.8 sat/vB on the first sweep and 4.80 sat/vB on the second.

Weak Keys

No identifiable person or entity has been tied to the incident, with no named victim, known bot operator, or public explanation for why someone built a wallet on a key pulled from a block's coinbase transaction. Similar RBF bidding wars have reportedly occurred on other weak-key addresses, including some with larger sums.

Implications

For bot operators, the economics look shaky. Spending roughly 380 times the value of the prize is not sustainable. Such losses limit profitability, potentially forcing operators to add stop-loss logic that caps how much they will pay to win a sweep.

Miners emerge as the quiet beneficiaries, doing nothing unusual beyond including the highest-paying transactions. RBF, designed to help users speed up stuck transactions, becomes a fee escalator that transfers value directly to block producers when used by competing bots.