Facebook, LinkedIn and other online services have been resetting accounts after 2 million login credentials, apparently stolen from users' computers, were discovered on a server in the Netherlands.
Payroll processor ADP said Wednesday it has reset the passwords of 2,400 clients but did not believe its internal network was compromised. Facebook, LinkedIn and Twitter have also reset some user accounts.
Security company Trustwave said on Tuesday its SpiderLabs research group gained access to an administrator control panel for the server, which was part of a botnet called "Pony" that collected sensitive information from users in as many as 102 countries. Trustwave said it notified the affected organizations. Some of the credentials were outdated.
ADP said it reset the accounts after it became aware of a phishing campaign. Phishing involves tricking people into divulging their login credentials or into installing malicious software, which harvests credentials and sends them to an attacker.
"To our knowledge, none of ADP's clients has been adversely affected by the compromised credentials," ADP said in a statement.
Facebook said it had reset passwords for its affected accounts.
"While details of this case are not yet clear, it appears that people's computers may have been attacked by hackers using malware to scrape information directly from their web browsers," according to a company statement.
Facebook said users can activate two features, "Login Approvals" and "Login Notifications," which let them know if their account was accessed from a different Web browser and require a one-time passcode sent to their mobile phone to access the site.
LinkedIn said it invalidated the credentials that matched the ones Trustwave discovered. "We've already been working with Spiderlabs to reset the passwords of the accounts whose LinkedIn credentials were on the list," a spokeswoman wrote via email.
A Twitter spokesman said the company reset some accounts after it was in touch with Trustwave last week.
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