A hacker is advertising what he says is more than one hundred million LinkedIn logins for sale.
The IDs were reportedly sourced from a breach four years ago, which had previously been thought to have included a fraction of that number.
At the time, the business-focused social network said it had reset the accounts of those it thought had been compromised.
LinkedIn now plans to repeat the measure on a much larger scale.
One expert said the service should have reset all its accounts the first time round.
LinkedIn is often used to send work-related messages and to find career opportunities – activities its members would want to stay private.
Criminals could make use of this information or see if its subscribers had used the same passwords elsewhere.
“We are taking immediate steps to invalidate the passwords of the accounts impacted, and we will contact those members to reset their passwords,” a spokeswoman for the California-based firm told the BBC.
Source: Millions of hacked LinkedIn IDs advertised ‘for sale’ – BBC News