It's the "most inclusive" bug bounty program to date, meaning that foreign nationals — except those from China, Russia, Iran or North Korea — are welcome to participate.

DOD tapped cybersecurity firms Synack, HackerOne and Bugcrowd to provide vetted hackers for continual assessments of defense websites, hardware and physical systems.

The department recently joined the trend of federal bug bounty programs, which boost cybersecurity resources in ways that traditional methods probably can't.

The Hack the Marine Corps program launched Aug. 12 with a live hacking event in Las Vegas.

"Assets could include closed networks, software-embedded devices, proprietary source code, or other private or internal systems not generally accessible via the public Internet," a new RFI says.

This time the Pentagon wants hackers to find vulnerabilities in the Defense Travel System's public-facing websites.