North Korean cybercriminals stole more than $20 million in cryptocurrency from a leading Indonesian exchange last week, according to Indonesian state media, engineering more than a hundred virtual transactions to stealthily move the illicit funds.

Oscar Darmawan, the chief executive officer of the Indodax exchange, said in a statement that the attackers took advantage of apparent security lapses to potentially steal “several hundred billions of [Indonesian] rupiahs,” national news agency Antara reported on Saturday.