Sept. 2 (Bloomberg) -- Gen. Keith Alexander (Ret.), former director of the NSA, comments on the escalating situation in Ukraine. He speaks with Trish Regan on "Street Smart." (Source: Bloomberg)

Hackers who stole gigabytes of data from JPMorgan Chase & Co. may have been trying to send a message that U.S. financial institutions can be disrupted, the former director of the National Security Agency said.

The FBI is investigating the cyberattack on JPMorgan and whether other banks were penetrated in retaliation for U.S.- backed sanctions on Russia, according to people familiar with the investigation who asked not to be identified because the probe is still underway.

Graphic: Data Breaches in the U.S.

Keith Alexander, the NSA director from 2005 until last March, said he had no direct knowledge of the attack though it could have been backed by the Russian government in response to sanctions imposed by the U.S. and EU over the crisis in Ukraine.

Securing the Net

How would you shake the United States back? Attack a bank in cyberspace, said Alexander, a retired U.S. Army general who has started his own cybersecurity company to sell services to U.S. banks. If it was them, they just sent a real message: Youre vulnerable.

As NSA chief and head of the U.S. Cyber Command, Alexander tracked and tried to thwart international hackers, giving him knowledge of their tactics. He was head of the NSA in 2008 when the country of Georgia was invaded by Russia and experienced a series of disruptive cyberattacks believed to be the work of Russian hackers.

Keith Alexander, former director of the National Security Agency and former commander of U.S. Cyber Command, speaks during a Bloomberg Television interview in Washington, on June 3, 2014. Close

Keith Alexander, former director of the National Security Agency and former commander... Read More

Read the original post:

Former NSA Chief Says JPMorgan Hack May Be a Warning