Passwords that took seconds to guess, or were never changed from their factory settings. Cyber vulnerabilities that were known, but never fixed. Those are two common problems plaguing some of the Department of Defense's newest weapons systems, according to the Government Accountability Office.The flaws are highlighted in a new GAO report, which found the Pentagon is "just beginning to grapple" with the scale of vulnerabilities in its weapons systems. Drawing data from cybersecurity tests conducted on Department of Defense weapons systems from 2012 to 2017, the report says that by using "relatively simple tools and techniques, testers were able to take control of systems and largely operate undetected" because of basic security vulnerabilities. The GAO says the problems were widespread: "DOD testers routinely found mission critical cyber vulnerabilities in nearly all weapon systems that were under development."When weapons program officials were asked about the weaknesses, the GAO says, they "believed their systems were secure and discounted some test results as unrealistic."The agency says the report stems from a request from the Senate Armed Services Committee, asking it to review the Pentagon's efforts to secure its weapons systems. The GAO did so by going over data from the Pentagon's own security tests of weapon systems that are under development. It also interviewed officials in charge of cybersecurity, analyzing how the systems are protected and how they respond to attacks. The stakes are high. As the GAO notes, "DOD plans to spend about $1.66 trillion to develop its current portfolio of major weapon systems." That outlay also comes as the military has increased its use of computerized systems, automation and connectivity. Despite the steadily growing importance of computers and networks, the GAO says, the Pentagon has only recently made it a priority to ensure the cybersecurity of its weapons systems. It's still determining how to achieve that goal — and at this point, the report states, "DOD does not know the full scale of its weapon system vulnerabilities."Part of the reason for the ongoing uncertainty, the GAO says, is that the Defense Department's hacking and cyber tests have been "limited in scope and sophistication." While they posed as hackers, for instance, the testers did not have free rein to attack contractors' systems, nor did they have the time to spend months or years to focus on extracting data and gaining control over networks.Still, the tests cited in the report found "widespread examples of weaknesses in each of the four security objectives that cybersecurity tests normally examine: protect, detect, respond, and recover."From the GAO: