How vulnerable is the U.S. to a cyber-attack?  Experts say it's now become the number one threat to the nation's security, but New Jersey is taking steps to protect crucial information.

While there hasn't been a full-scale cyber-attack here yet, that doesn't mean terrorists from other countries aren't looking to inflict massive damage, said FBI director Robert Mueller.

He testified at a recent House appropriations subcomittee hearing that while hackers have not used the Internet to launch a full-scale cyber attack, the bureau cannot underestimate the intent of terrorists to do so.

"The internet is incredibly valuable, but easy to hack" said James Lewis, senior fellow at Center For Strategic & International Studies.

Lewis said the U.S. needs to improve communication with other countries to help prevent retaliation from such acts occurring.

"The clock is ticking, though.  If Iran or China get ahold of our nation's power-grid or hack into our computer systems they could do some major damage."

He blames the threat on those looking to send a strong message to the U.S., mainly motivated by politics.

"A lot of people dislike our country and our looking to do us harm so this is something they would try...they could hack into a power-grid or put a city in complete darkness."

But he said a cyber-attack would not result in mass casualties.  "There wouldn't be loss of life or anything along those lines...but it could prove very disruptive to our country."

Based on FBI suggestion, the New Jersey Board of Public Utilities recently took steps to safeguard electric, gas and water companies around the state.  They ordered the utilities to outline what equipment and measures they have in place to monitor against cyber-intrusions.

Lewis said this week a group of U.S. senators are taking part in a mock black-out based on a cyber-attack.  "It will be interesting to see what comes out of that event and what lessons they learn."