Enormous Equifax data breach hits 143 million
UK consumers also affected
A credit-rating firm holding data on more than 820million consumers and 91 million businesses has been hacked.
According to a BBC report, the Equifax breach is one of the largest ever reported in the US.
About 143million American customers are believed to have had information compromised, with some UK and Canadian consumer also affected.
Equifax said cyber-criminals accessed data such as Social Security numbers, birth dates and addresses and credit card numbers during the incident. The company said malicious hackers gained access to its systems by exploiting a "website application vulnerability", but provided no further details.
Equifax said it would work with regulators in the US, UK and Canada on next steps. It is also offering free credit monitoring and identity theft protection for a year.
It has set up a website for consumers to check if their data has been caught up in the breach. However, many people trying to visit the site reported that they had problems accessing it and that security software flagged it as potentially dangerous.
The UK's Information Commissioner (ICO) told the BBC that reports about the data breach and the potential involvement of UK citizens gave it "cause for concern".
It said it was in contact with Equifax to find out how many British people were affected and the kinds of data that had been compromised.