Washington and many international corporations have long suspected that the Chinese government is largely behind the chronic cyberattacks that have bedeviled many companies. A recent report by a private security firm, Mandiant Corp., has left little doubt.

The administration should make it clear to Beijing that this behavior is unacceptable and that if it continues, it could threaten a relationship that involves the trade of $425 billion a year.

Mandiant not only verified that China was behind hackers that have stolen huge amounts of data and trade secrets, it traced the source of the attacks to a building on Datong Road in Shanghai — the headquarters of People’s Liberation Army Unit 61398.

The attacks have been mainly aimed at commercial targets. In the case of two newspapers, hackers apparently were trying to learn identities of reporters’ sources.

In one respect, it’s a sad comment on China today. It has evidently reached a point in its development where it can’t continue its breakneck growth rate simply by following the trail blazed by others, such as greater scope for free markets and export-led growth. It has reached the point where it must have access to the latest technology, but instead of innovating on its own, it attempts to steal the innovations of others.

The national security implications are also serious. China, as well as other countries, have shown a disturbing ability to gain access to critical U.S. computer networks such as those that coordinate air traffic control and power grids. What isn’t publicly known is how successful they have been at breaching our military networks.

So far, the Obama administration has been reserved in its handling of this problem. For example, The New York Times reports that privately, administration officials don’t dispute the Mandiant conclusions, but they have no desire to say this on the record for fear embarrassing Beijing could backfire.

A firmer stance is in order. If the data thefts and cyberattacks continue, Washington must put other measures on the table, including sanctions targeting the people and entities behind the attacks.

The above editorial appeared in the Kansas City Star on Friday, March 1.