South Korea’s National Tax Service (NTS) mistakenly published a cryptocurrency wallet mnemonic in an official press release, and thieves used it to drain about 4 million PRTG (Pre‑Retogeum) tokens — roughly $4.8 million — from the exposed address, local media reported.
The release, describing the NTS’s enforcement actions against tax delinquents and asset seizures, included an image showing a Ledger cold wallet next to a sheet of paper that displayed the wallet’s full mnemonic seed phrase with no blurring or masking. Blockchain researchers traced an Ethereum address derived from the leaked phrase; that address briefly received three inbound transfers totaling 4 million PRTG before the entire balance was moved out in a single outbound transfer.
Jaewoo Cho, an associate professor at Hansung University’s Blockchain Research Center who analyzed the token flows, said the 4 million PRTG — about $4.8 million — were stolen after the mnemonic was disclosed in the press release. He noted that other mnemonics published by the NTS do not appear likely to cause major losses and suggested that because the stolen tokens are difficult to cash out, the practical damage may be limited. Cho said he hoped the incident would prompt public agencies in Korea to adopt proper virtual-asset custody systems.
The error adds to growing scrutiny of Korean authorities’ crypto custody practices. In a separate February 2026 case, investigators found that 22 Bitcoin seized in a 2021 hacking probe had gone missing from a cold wallet stored in a Gangnam police vault; authorities arrested two suspects after determining the coins were moved using a mnemonic the police never controlled.
Regulators and institutions have faced other high-profile mistakes as well, including a Bithumb incident that briefly showed users credited with about 620,000 BTC (roughly $43 billion in non-existent Bitcoin) and an extended probe by the Financial Services Commission after criticism that it had not identified serious system flaws sooner.
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