ICBC Financial Services said it is recovering from a cyber attack that disrupted its systems and forced employees to trade with USB sticks. ICBC FS is the US unit of China’s biggest bank and the world’s largest commercial lender by total assets.

The attack rendered the bank unable to clear many US Treasury trades and caused it to temporarily owe BNY Mellon $9bn (£7bn). It could only return the debt after a cash injection from its Chinese parent.  

ICBC has said it is working with cyber-security firm MoxFive to set up secure systems that would allow it to resume normal business on Wall Street. However, the disruption caused by the hack has raised concerns about the resilience of the $26tn (£21tn) Treasury market.

“Immediately upon discovering the incident, ICBC FS disconnected and isolated impacted systems to contain the incident,” the bank said. It added that it is “progressing its recovery efforts with the support of its professional team of information...