A branch of the U.S.’s central bank is forcing a password reset after a cyberattack briefly redirected visitors to parts of its website to bogus Web pages.

The Federal Reserve of St. Louis found on April 24 that DNS (domain name system) settings had been changed to redirect people to fake Web pages. The bank didn’t name its DNS provider. Those who visited those pages may have been exposed to malware or had their login credentials stolen.

“If you attempted to log into your user account on that date, it is possible that this malicious group may have accessed your user name and password,” an advisory said.

The DNS is a global database that resolves domain names into IP addresses that can be called into a browser. Those who run DNS networks guard them carefully, as modifications can send people to the wrong website.

DNS hacks are powerful since a person can be directed to a different IP address even if they type in the correct domain name.

The bank said the rogue webpages were designed to look like its research website. Other fake webpages were created that mimicked those in the research site, which contains databases of economic information.