Companies can't keep your data safe. It's that simple.

When Target lost data on some 110 million customers, it recommended them to credit bureau Experian for "identity theft protection," offering to cover the cost for a year.

Think you're in better hands? Think again.

Sometime before the Target (TGT) hack, Experian had its own data leak -- via a subsidiary. That data leak got plugged before Target sent victims to Experian. But it shows that even those entrusted with our most sensitive data don't know how to protect it.

Experian unknowingly sold the personal data of millions of Americans -- including Social Security numbers -- to a fraudster in Vietnam. That guy then sold the personal information to identity thieves around the globe.

It wasn't until U.S. Secret Service agents alerted Experian that the company stopped.

Related story: Why retailers aren't protecting you from hackers

Hieu Minh Ngo, now 25, was caught and admitted to posing as a private investigator in Singapore to get exclusive access to data via Court Ventures, an Experian subsidiary. Ngo then sold access to fellow criminals.

Federal investigators say that let criminals reach databases with hundreds of millions of Americans' personal data, including:

names

addresses

Social Security numbers

birthdays

work history

driver's license numbers

email addresses

banking information

Criminals tapped that database 3.1 million times, investigators said. Surprised you haven't heard this? It's because Experian is staying quiet about it.

It's been more than a year since Experian was notified of the leak. Yet the company still won't say how many Americans were affected.

CNNMoney asked Experian to detail the scope of the breach. The company refused.

"As we've said consistently, it is an unfortunate and isolated issue -- one that did not affect Experian's databases and has no true relevance to the work we did with clients like Target," Experian spokesman Gerry Tschopp said.

Federal court filings show that at least one database actually belonged to another firm -- U.S. Info Search. It was Experian's subsidiary that sold database access to Ngo.

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Target and Experian insist that the credit monitoring service is unrelated to the incident involving Experian's data-selling business.

But even Experian's credit monitoring service, which collects data on customers, isn't immune.

According Barry Kouns, a security professional who maintains a Cyber Risk Analytic database of major data breaches, said Experian's databases have been involved in 97 breaches of personal information.

"Based on our research, it appears that data brokers place a high value on collecting and using our information but not so much on protecting it," Kouns said.