China’s biggest lender, the Industrial and Commercial Bank of China, paid a ransom after it was hacked last week, a Lockbit ransomware gang representative said on Monday in a statement which Reuters was unable to independently verify.

ICBC, whose US arm was hit by a ransomware attack that disrupted trades in the US treasury market on 9 November, did not immediately respond to a request for comment.

“They paid a ransom, deal closed,” the Lockbit representative said via Tox, an online messaging app.

The blackout at ICBC’s US broker-dealer left it temporarily owing BNY Mellon US$9-billion, an amount many times larger than its net capital.

The hack was so extensive that even corporate e-mail at the firm ceased to function, forcing employees to switch to Gmail. “The market is mostly back to normal now,” said Zhiwei Ren, a portfolio manager at Penn Mutual Asset Management.

The ransomware attack came at a time of heightened worries about the resiliency of the $26-trillion treasury market, essential to the plumbing of global finance, and is likely to draw scrutiny from regulators.

A spokesman for the US treasury department did not immediately provide comment on Monday.

Protocols

The Financial Services Information Sharing and Analysis Center, a financial industry cybersecurity group, said financial firms have well-established protocols for sharing information on such incidents.

“We are reminding members to stay current on all protective measures and patch critical vulnerabilities immediately,” a spokesman said in a statement, adding: “Ransomware remains one of the top threat vectors facing the financial sector.”

Lockbit has hacked some of the world’s largest organisations in recent months, stealing and leaking sensitive data in cases where victims refused to pay ransom.

Read: 40 countries vow not to pay ransomware attackers

In just three years, it has become the world’s top ransomware threat, according to US officials.

Nowhere has it been more disruptive than in the US, hitting more than 1 700 American organisations in nearly every sector from financial services and food to schools, transportation and government departments.

Authorities have long advised against paying ransomware gangs in a bid to break the criminals’ business model. Ransom is usually demanded in the form of cryptocurrency, which is harder to trace and gives the receiver anonymity.

Some companies have quietly paid up in a bid to get back online quickly and avoid the reputational damage of having their sensitive data publicly leaked. Victims who do not have digital backups that allow them to restore their systems without the need of a decryption key sometimes have no choice but to pay.

Last week, Lockbit hackers published internal data from aerospace giant Boeing and said on their website they had infected computer systems at law firm Allen & Overy. — James Pearson, with Davide Barbuscia, Carolina Mandl, Tatiana Bautzer and Pete Schroeder, (c) 2023 Reuters