A spokesman for the U.S. Army Corps of Engineers today downplayed the significance of a recent incident of unauthorized access to a database containing potentially sensitive information on thousands of high hazard dams across the country.

The unauthorized access to the National Inventory of Dams (NID) was granted in January to an individual that fraudulently obtained login credentials. The access was revoked later that month when the Corps of Engineers discovered the subterfuge.

The spokesman said that the individual had access to "data reserved for government users, per agreement among NID participating agencies."

However, he contended that the information accessed doesn't present a threat to the public or critical infrastructure, he said.

"Upon learning that the user was not authorized governmental-level access to the NID, USACE revoked the user's access to the database," the spokesman said.

He referred further questions on the intruder's identity and how the unauthorized access was discovered, to U.S. Army Public Affairs.

A spokeswoman there said the Army is still reviewing the incident and is in the process of deciding how much information can be released.

The NID contains information on over 40,000 dams classified as being either high hazard or significant hazard, or where a failure could result in potential loss of human life and significant property damage.

Dams that are 25 feet or higher and those that exceed 50 acres-feet of storage capacity are also listed in the NID.

Registered non-government users can query portions of the database but are prohibited from downloading any data. Certain sections holding non-aggregated, dam-specific information are available only to government employees and contractors.

It is unlikely that information contained in the database by itself is critically sensitive said Ken Westin, a researcher at security vendor Tripwire.

However, when combined with other data elements, the information in the database could help attackers piece together a comprehensive understanding of potential weaknesses in U.S. dams, he cautioned.

"I am guessing they only provide usernames and passwords to access to the data on a need to know basis," Westin said. "The problem is that they are relying on usernames and password to identify the user."

It's likely that login credentials could have been provided to someone posing as a contractor or a government employee with legitimate access to the data. "No matter what security measures you have in place, what compliance or standards, if people are involved there will always be increased risk," he said.

The NID system has a password reset mechanism that could have been used by the attacker to reset the password of someone who had a high level of access to the contents of the database, he said.

Generally speaking, putting sensitive data in a system that is accessible via the Web is a bad idea, Westin said.

Even if sensitive data is segregated and available only to authorized users, someone with access to the public portion of the database can find a way to break into restricted area, he said.

"If you want to keep data secure, don't put it online," Westin said.

Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan, or subscribe to Jaikumar's RSS feed . His e-mail address is jvijayan@computerworld.com.