In March, a hacker broke into free-to-play gaming site Gamigo servers. The hacker took usernames, e-mail addresses, and passwords for an undisclosed number of users, posting a smattering of the data on the company's forums.

Three months later, someone posted the more than 8 million records on a password cracking forum, including accounts connected to employees with e-mail addresses from major companies such as IBM, Deutsche Bank, and ExxonMobil. Such leaks have become more common, leading a group of security experts to compile such public lists into a service, PwnedList. While the basic service -- checking to see whether an account linked to a single e-mail address -- is free, companies can benefit by checking to see whether their employees or their users have compromised accounts, says Steve Thomas, co-founder of the Austin, Texas-based PwnedList.

"We monitor for domains for companies that are worried about their internal security and their employees, but we have had quite a bit of push from people that we have been talking to -- corporations -- to enable them to monitor their end users," he says. "They can use us as their stolen credential blacklist."

The company has had no shortage of leaked account lists to collect. Founded in July 2011, the firm had gathered data from less than 400 leaks at the end of last year. Nine months later, the company has account lists from more than 1,000 leaks and is adding 150 new lists every month. Known sites for dumping account lists are checked every 10 minutes, while new ones are hunted down every hour.

While no leaks have been nearly as big as Gamigo -- even Sony's massive breach of up to 75 million records "only" resulted in 1 million leaked accounts -- hacktivism made 2011 a banner year for leaked account data, accounting for more stolen data than organized crime.

For companies, keeping track of the leaks and collating the data on their own is difficult, but they also might miss harvesting some of the data. The data on Gamigo's users, for example, has been taken down and is no longer available. Frequently, leaks posted to Pastebin get removed quickly as well.

"We get access to data leaks that the vast majority of hackers don't know about," Thomas says. "We can never say that we have 100 percent coverage. But in terms of a really reliable source, we are beating out the harvesting capabilities of quite a few security teams out there."

[ Three major online consumer services have acknowledged that their systems were breached and passwords leaked -- a litany of incidents that should remind companies to take another look at how they are managing and monitoring the access to their systems. See Keep Watch On Accounts For Stolen Passwords. ]

The service has gotten the jump on other breach-related services, such as AllClearID and Lifelock, which tend to offer services to consumers worried about their identities, but are more popular as a one-stop shop for companies that have already been breached.

In September, identity and password management service LastPass announced it would be using the PwnedList service to identify its users of potentially stolen accounts. In the future, all identity and access management services will likely start using such offerings, says Amber Gott, a spokeswoman for LastPass.

"A percentage of our users are active in the security space and might be able to scan these [known] forums for the lists, but the average user or IT manager is not going to want to do that," she says. "This is a way to take important aggregated information and alert the user almost immediately."

While the service can protect employees and customers from attackers who use published lists to hack, the coverage of the list is fairly sparse. Hacktivists tend to publish credentials they uncover in their attacks, but cybercriminals only sell the lists on underground markets, which won't be collected by PwnedList. In 2011, hacktivists stole 100 million of the estimated 174 million account records documented by Verizon Data Breach Investigations Report.

"It's not a problem that anyone can deal with with conventional means," Thomas says. "We're really going after the main problem of all these credentials that are leaked -- tens of millions each year. We are trying to help people understand if they are impacted."

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