Stolen credit card account numbers continue to flood the underground, but cybercriminals are starting to swipe other more lucrative data as these stolen accounts become more of a commodity.

Researchers at Finjan recently discovered 500 megabytes’ worth of a different kind of booty sitting on servers located in Argentina and Malaysia: Citrix single sign-on credentials for accessing patient and financial data at a major U.S. hospital and major healthcare organization; and similar credentials for accessing a large U.S. airline carrier’s passenger and cargo lists, flight schedules, security measures, and financial data.

Finjan's research illustrates that the bad guys are looking for different and more lucrative data that they can steal and then sell online to the highest bidder, says Yuval Ben-Itzhak, CTO of Finjan.

“It’s supply and demand. The fact is these people are now going after data that’s different from [the standard] credit card and SSN,” Ben-Itzhak says. “A year ago, a [stolen] credit card was $100. Now you can get one for $10-$20 a card.”

But that doesn’t mean cybercriminals still aren’t pilfering credit card data, other security experts argue. “I don't think there is a shift in cybercriminals stealing data other than credit card numbers. The stolen data from popular and mainstream Trojans is mainly grabbed via keylogging -- everything is captured, [and] then the wheat is separated from the chaff,” says Guillaume Lovet, senior manager for Fortinet’s Threat Response Team.

Lovet says the cybercriminals behind the servers Finjan found may not have even been after the login credentials, nor is it clear that the credentials are especially valuable. “The bottom line is that cybercriminals tend to capture all the data residing or transiting through compromised computers, [and] then sell everything there is a buyer for,” he says.

“Are there a lot of buyers for internal login credentials? [It] depends," Lovet says. "I may be wrong, but building a business based on buying/selling prescription drugs via ‘medical records’ hacking seems complicated, risky, and not significantly more profitable than messing with, say, eBay or Paypal accounts.”

Cybercriminals’ quest for more lucrative data to steal and sell is no surprise, experts say. “The scope of the credit card problem garners attention, but hackers have long been after any data of value,” says Randy Abrams, director of technical education for Eset.

Finjan also found stolen Social Security numbers and a health care organization employee’s Outlook email account credentials.

Meanwhile, Ben-Itzhak says he’s not sure exactly how the victims initially got infected, but it could have been via spam or visiting an infected Website. “We are aware of several Websites infected with this malicious code,” Ben-Itzhak says. It probably began with a doctor or other employee visiting such a site and his machine getting infected with the keylogger and other malware, he says.

The servers use the so-called ZeUs Trojan, which does keylogging, takes screen shots of the victim’s machine, and can poison legitimate Websites, according to Finjan's report on its findings.

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