Researchers at cybersecurity firm Trustwave in a recent report released this week said hackers have stolen usernames and passwords for nearly two million accounts at Facebook, Google, Yahoo, Twitter, and others.
The massive data breach was a result of a keylogging software that got maliciously installed on a large number of computers around the world. The virus was capturing log-in credentials for popular websites like Facebook, Twitter and others over the past month and sending those usernames and passwords back to a server controlled by the hackers.
Trustwave researchers tracked that server on Nov. 24, and traced its location in the Netherlands. They discovered compromised credentials for more than 93,000 websites, including:
318,000 Facebook (FB, Fortune 500) accounts
70,000 Gmail, Google+ and YouTube accounts
60,000 Yahoo (YHOO, Fortune 500) accounts
22,000 Twitter (TWTR) accounts
9,000 Odnoklassniki accounts (a Russian social network)
8,000 ADP (ADP, Fortune 500) accounts (ADP says it counted 2,400)
8,000 LinkedIn (LNKD)accounts
Trustwave has notified these companies of the breach and posted their findings to the public on Tuesday.
"We don't have evidence they logged into these accounts, but they probably did," said John Miller, a security research manager at Trustwave.
Facebook, ADP, LinkedIn and Twitter said they have notified and reset passwords for compromised users. Google (GOOG, Fortune 500) declined to comment while Yahoo is yet to provide a response.
Miller said the team doesn't yet know how the virus got onto so many personal computers. The hackers set up the keylogging software to rout information through a proxy server, so it's impossible to track down which computers are infected.
Among the compromised data are 41,000 credentials used to connect to File Transfer Protocol (FTP, a standard network used to transfer large amounts of data) and 6,000 remote log-ins.
The hacking campaign began secretly collecting passwords on Oct. 21, and is believed to be ongoing: Although Trustwave discovered the Netherlands proxy server, Miller said there are several other similar servers they haven't yet tracked down.
The researchers say the virus is hidden and runs in the backgroung making it hard to detect. So, just searching through programs and files to find it won't be enough if you want to know if your computer is infected, Miller said. Update your antivirus software and do a safe download for the latest versions for Internet browsers, Adobe (ADBE) and Java. This is absolutely essential if your computer does not run on a linux operating system.
Miller said he is most concerned with ADP as those log-ins are typically used by payroll personnel who manage workers' paychecks. Any information they see could be viewed by hackers until passwords are reset.
"They might be able to cut checks, modify people's payments," Miller speculated.
ADP said in a statement released that, "To its knowledge, none of ADP's clients has been adversely affected by the compromised credentials."