SAN FRANCISCO -- Were state-sponsored Russian hackers behind the coordinated cyber attacks that looted data from JPMorgan Chase and other banks this month?

The sophistication of the attacks suggests a government connection, said Phil Lieberman, CEO of Lieberman Software.

Russia is sending a message through proxies, he said.

"The ability to overcome the typical financial defense-in-depth strategy outlined by JPMorgan points to capabilities that go beyond criminal activity and are in the realm of nation state capabilities," Lieberman said.

The FBI is investigating whether the attack could have been in retaliation for U.S. sanctions on Russia. At least one of the banks has connected Russian hackers to the attacks, according to published reports.

The attacks come as tensions mount between the U.S. and Russia over sanctions that have damaged the Russian economy.

Attacks on the U.S. financial sector from Russia and Eastern Europe have increased in recent months, suggesting a link to the conflict over Ukraine, security experts say.

U.S. and European sanctions have changed the way banks deal with Russian transactions. In April, JPMorgan blocked a payment from a Russian embassy. Russia's foreign ministry called the move "illegal and absurd."

Cyber security intelligence firm ISight Partners recently warned clients that sanctions could lead to retaliation.

But some security experts say they can't yet rule out the possibility that the attacks were the work of wily cyber thieves who launch attacks daily on U.S. interests.

"Russian hackers are known for being the best in the industry," said John Gunn, vice president of corporate communications for VASCO which provides security to the banking industry. "These hackers aren't generally politically motivated. Their only loyalty is to profit."

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