As the nation continues to reel from the terrorist attacks in Boston, Twitter has demonstrated America's vulnerability on an entirely different front.

Hackers were able to send out a tweet from the account of the Associated Press this week announcing a bogus story about explosions at the White House. Within seconds, a massive sell-off on Wall Street instantly erased $134 billion in stock values.

The markets recovered and no permanent damage was done, but this experience provided a valuable lesson in just how exposed America's information network is. The sell-off happened so quickly because computers, not human beings, instigated all of the trades. Much of the country's wealth exists solely in cyberspace, and penetrating online financial systems could create chaos in world markets that would have devastating long-term consequences across the globe.

And it's not just money. So much of our military power depends on the integrity and security of our state-of-the-art technology and information systems. Imagine a hacker gaining virtual access to the Department of Defense. Are there enough safeguards in place to prevent someone from disabling our capacity to respond to threats?

Experts say no. A 138-page report issued by the Department of Defense at the beginning of this year outlines the very real danger of a cyber attack and the unpreparedness of the United States to respond. Tools that can be readily accessed online by anyone with an Internet connection were successfully used in simulations to disrupt military readiness.

From the report: "These stark demonstrations contribute to the task force's assertion that the functioning of DOD's systems is not assured in the presence of even a modestly aggressive cyber attack."

This isn't just academic. South Korea recently had to ward off a heavy cyber assault from its neighbors to the North. The DOD report warns of the possibility of a "full-spectrum opponent" that could use a weakened information network to amplify its own military assault on the United States. Given the daunting power of the United States military, it's very likely that a prospective enemy would rely on cyber terrorism to get the United States to involuntarily lower its guard.

These are frightening, dire scenarios, to be sure, but they don't have to become reality. Thankfully, this latest incident via Twitter isn't likely to have many lingering effects. But it definitely is a wake-up call. The nation needs to do more to protect itself from all enemies, real and virtual.