A ransomware attack on a US unit of the powerful Industrial and Commercial Bank of China that may have contributed to a brief market sell-off on Thursday was a significant escalation for cybercriminals that underscored how big hacks can disrupt business for even the best-resourced companies, experts told CNN.

The incident immediately sparked concern among regulators and senior US and Chinese officials. It led to a flurry of behind-the-scenes coordination with the affected bank and across the financial sector about the threat.

FS-ISAC, an industry group for sharing cyberthreat intelligence composed of big banks around the world, has been sharing data on the attack with its members and reminding them “to stay current on all protective measures and patch critical vulnerabilities immediately,” a spokesperson for the group told CNN on Friday.