Analysis: Arbitrum Freezes KelpDAO Hacker's ETH in System-Level Transaction, Injected via ArbOS by Security Council

On April 21st, Dragonfly General Partner Haseeb Qureshi published an analysis of the Arbitrum Security Council’s freeze of 30,766 ETH belonging to the KelpDAO hacker. Key details from the analysis: - The transaction was an **ArbitrumUnsignedTxType** (EIP-2718 type 0x65/101) — a system-level transaction that regular EOAs cannot sign, and only the Arbitrum Security Council can inject via ArbOS. - This action did **not** involve chain rollbacks or historical state rewrites; it was a *state-level clawback*: the hacker’s private key still works for signing transactions, but the ETH in their address was moved by the chain itself. - The operation showcased the Security Council’s authority in the "catastrophic emergency" scenario outlined in Arbitrum’s progressive decentralization documentation.