The optimistic outlook is that the internet of things will be an enabling technology that will help make the people and physical systems of the world — health care, food production, transportation, energy consumption — smarter and more efficient.

The pessimistic outlook? Hackers will have something else to hack. And consumers accustomed to adding security tools to their computers and phones should expect to adopt similar precautions with internet-connected home appliances.

“If we want to put networked technologies into more and more things, we also have to find a way to make them safer,” said Michael Walker, a program manager and computer security expert at the Pentagon’s advanced research arm. “It’s a challenge for civilization.”

To help address that challenge, Mr. Walker and the Defense Advanced Research Projects Agency, or Darpa, created a contest with millions of dollars in prize money, called the Cyber Grand Challenge. To win, contestants would have to create automated digital defense systems that could identify and fix software vulnerabilities on their own — essentially smart software robots as sentinels for digital security.

A reminder of the need for stepped-up security came a few weeks after the Darpa-sponsored competition, which was held in August. Researchers for Level 3 Communications, a telecommunications company, said they had detected several strains of malware that launched attacks on websites from compromised internet-of-things devices.