The Defense Advanced Research Projects Agency is working on what it calls the "four big things" to protect U.S. military technology from hackers.

Cybersecurity is the latest big deal in military affairs. It's one of the few growing areas of the nation's defense budget at a time when most line items are shrinking, because of concerns about hacking by foreign powers.

The Justice Department on May 19 unveiled indictments against five Chinese military officials for spying on U.S. companies.

Here is a rundown of DARPA's "four big things:"

1. High-Assurance Cyber Military Systems, or HACMS (pronounced "Hack 'Ems")

Military computers, like personal computers, must be updated periodically to patch security vulnerabilities. This poses a problem when the computer in question is being used — for example, when it is embedded in a plane flying at 30,000 feet.

HACMS are computers designed so they do not require security updates. At Demo Days, DARPA unveiled a HACMS prototype to thwart cyberattacks on unmanned aerial vehicles. The prototype has been touted as a "hack-proof" drone.

2. The Cyber Grand Challenge

DARPA is programming antivirus software that will evolve to combat emerging threats. The goal is to develop software smart enough to beat human hackers, who often bypass antivirus software by making minor changes to existing viruses.

Dan Kaufman, director of DARPA's Information Innovation Office, says this is not an idea out of the realm of science fiction: "Just ask [Jeopardy champion] Ken Jennings how well he does [against Watson]," Kaufman said.

Similar to the non-profit X Prize Foundation, DARPA's inaugural Cyber Grand Challenge offers a substantial cash reward to the team of programmers that creates the best automated security system.

3. Computer Individuality

Currently, a single well-designed virus can infect millions of computers by exploiting their uniformity. DARPA hopes to contain the spread of such attacks by developing computers that are distinct from one another, yet similar enough to be networked and mass-produced. If DARPA succeeds, hackers who wish to compromise a network of computers will have to program a new attack for each of its constituent parts.

Kaufman likens this technology to the human immune system, which varies minutely from person to person. The immune system helps avert disease epidemics; DARPA hopes it can use the same principle to avert digital disasters.

4. Advanced Encryption

Even if hackers weasel their way into a Defense Department system, soon their efforts may yield nothing but gibberish.

DARPA is working to develop a direct and unbreakable form of data encryption. The technique they are studying, called "fully homomorphic encryption" -- alternately called the "Holy Grail for computer scientists" -- was thought to be unattainable until a Stanford doctoral candidate proved otherwise. (Yes, he was awarded the degree.)