In the time it takes to read or listen to this sentence, more than 6,000 cyber attacks will be launched by terrorists and foreign countries against the U.S. government and American businesses. These attacks can be divided into three types:

• Cyber warfare
• Cyber espionage
• Cyber terrorism

Let's explore each of these threats.

Cyber warfare is an attack on one government by another government or large groups of individuals. In 2008, U.S. Director of National Intelligence Mike McConnell revealed in The New Yorker magazine that the Defense Department detects 3 million unauthorized probes of its computer networks every day. The same article reported that China has 40,000 hackers gathering U.S. intelligence from our computer networks.

An example of cyber warfare was the massive assault on Estonia's computer systems after the government decided to move a monument of a soldier dating from the Soviet era. Estonia's Russian citizens, and apparently the Russian government, were opposed to the move. On April 26, 2006, and for several days afterward, 1 million "zombie" computers bombarded government Web sites in Estonia with data so rapidly that the servers couldn't keep up. The sites affected included those of the country's president, prime minister, and parliament, where the deluge of data shut down the e-mail system.

What makes cyber warfare attacks so effective is the ability to unleash an overpowering attack by using a botnet, which is a network of computers that have been commandeered through a software program that allows them to be controlled remotely by a single computer.

According to James Jay Carafano, PhD, a Heritage Institute senior research fellow for national security and homeland security, many people unknowingly allow their computers to be taken over by clicking on pop-ups, and many others do nothing more than open a Web browser that has been compromised so that it stealthily downloads malicious code onto the user's hard drive.

The end result is an army of machines that can be programmed by a spy or terrorist. By directing thousands of computers to send data to targeted Web sites in a denial-of-service attack, the attacker can effectively shut down a computer network.

Cyber espionage is the use of digital technologies to gain access to sensitive data that can be used for competitive purposes. The trade secrets of businesses are often targeted, with one estimate putting the annual cost of corporate espionage to victims at $1.5 trillion.

Even more troubling is the threat of cyber espionage against the U.S. government. According to Spy-Ops, 140 countries and more than 50 terrorist and criminal groups are now using or developing tools for cyber espionage. For example, according to Kevin G. Coleman, consultant at the Technolytics Institute, China is suspected in the recent theft of the names, birth dates, and social security numbers of every visitor to the Oakridge National Laboratory between 1990 and 2004, including an unknown number of people with security clearances. Similar attacks have been made on the 10 biggest U.S. defense contractors, including Boeing, Northrup, Raytheon, and Grumman.

The most common and effective tool that digital spies use is "phishing," in which they persuade victims to give out information or convince them that an attachment to an e-mail comes from a trusted source.

Cyber terrorism is an attack by terrorists using a computer network to disrupt a Web site or an entire economy. This can be anything from using the Internet to post a threat about an upcoming attack in order to frighten people, to actually carrying out an attack using the Web.

Fortunately, terrorist groups such as Al Qaeda have so far used the Internet primarily as a vehicle for creating fear rather than for doing real damage. However, antiterrorism experts consider the threat of a cyber attack to be highly likely. In fact, a book commissioned by the National Academy of Sciences predicts, "Tomorrow's terrorist may be able to do more damage with a keyboard than a gun."

For example, according to InformationWeek, a program called the "Electronic Jihad" is a Web-based application that allows Islamic terrorists to attack Web sites that they perceive to be anti-Islamic. The application includes an interface that lets users select a Web site from a list provided by jihadis, decide whether to make the attack weak, medium, or strong, and then click on an "attack" button.

In addition, if terrorists could hack into a computer network controlling a region's power grid, it could shut down 70 percent of all economic activity, according to a Council of Foreign Relations report, citing economist Scott Borg of the nonprofit U.S. Cyber Consequences Unit.

Based on this assessment, the Trends editors offer the following four forecasts:

First, cyber attacks will continue to increase for the foreseeable future. Because awareness is still low relative to the threat, many companies' networks remain vulnerable to attacks. In addition, the American military is too strong for any foreign power or terrorist group to attack through conventional warfare, so our enemies will look for ways to disable our information networks.

Second, businesses will need to take costly steps to protect themselves from cyber warfare. In addition to training all users to avoid phishing scams and constantly updating security software, one extreme measure may be cost-effective in the long run: Use more than one computer system. For example, Cryptography Research, a business that provides security consulting to businesses and government agencies, protects itself from cyber attacks by using two independent computer networks. According to an article in Network World, the company uses one system for email and the Internet, and the other for internal communications. This means that every employee has to use two computers and the company buys twice as much software, but the company's president believes the security is worth the cost.

Third, the U.S. government will need to devote a growing number of resources and attention to protecting its information and networks from cyber terrorists and cyber spies. For instance, the Air Force Research Laboratory's Integrated Cyber Defense plan involves rewriting the laws for its computer networks. It intends to make hostile traffic inoperable on military networks, locate hackers, and make networks immune from electronic attacks. Also, the military is believed to have deployed a secret technology known as the Suter system, which can be carried aboard military spy planes and unmanned aircraft. It can penetrate enemy communications networks and take control of them.

Fourth, ultimately, the solution will emerge through innovation. Just as American businesses continue to develop new products as the economy shifts from manufacturing to knowledge-based products and services, and just as the military has transformed itself into a leaner, flexible force that can better respond to the new realities of warfare, the tools that will protect us from the threats of cyber warfare, cyber espionage, and cyber terrorism will be developed through the forces of creative destruction and free market competition.