Credit bureau firm Equifax has apparently suffered a significant data breach, with tax and salary data for more than 431,000 US workers being stolen from its systems.
The report of the leak comes via independent security researcher Brian Krebs, who claims to have seen a letter from American grocery firm Kroger to its employees, stating an unauthorised third party had accessed Equifax's W-2Express system, which lets individuals manage their W-2 tax forms (similar to a tax return in the UK) online.
"It appears that unknown individuals have accessed [Equifax's] W2Express website using default log-in information based on Social Security numbers (SSN) and dates of birth, which we believe were obtained from some other source, such as a prior data breach at other institutions," Kroger's letter said.
"Kroger is working with Equifax and the authorities to determine who is affected and restore secure access to W-2Express. At this time, we believe you are among our current and former Kroger associates using the default PIN in the W-2Express system. This does not necessarily mean your W-2 was accessed as part of this security incident. We are still working to identify which individuals' information was accessed," it added.
The company sought to reassure workers that its own systems have not been compromised, but admitted it does not know how many of them had been affected.
This is not the first time a data breach has affected Equifax's W-2Express systems, with Stanford University revealing in April that several hundred of its employees, past and present, had their details stolen.
IT Pro has contacted Equifax for its response to the allegations, but had not received a response at the time of publication.
