It’s hard to fathom, but the United States once chose 00000000 as the password for its computer controls of nuclear-tipped missiles, and it stayed that way for nearly 20 years. Strange, but true.
In 1962, John F. Kennedy signed the National Security Action Memorandum 160, which authorized that nuclear weapons had to have something called a Permissive Action Link, or PAL. This was a security device that would prevent unauthorized arming or detonation of intercontinental ballistic missiles (ICBM) without the correct code and correct authorization.
The reason for the PAL was to ensure that if some other government got hold of the nukes, they wouldn’t be able to launch them. It was also in place so that US military commanders couldn’t launch an ICBM by themselves, and the missiles would never be in the control of one person. The PAL was believed to be an extremely secure device if it was in place.
The problem occurred, as it often does with anything dealing with the government, that the military simply neglected to fit the PALs to many of the nuclear ICBMs. Half of the missiles in Europe continued to be secured only by mechanical locks. The missiles in the Minuteman silos in the United States were fit with a PAL under the direction of the Secretary of Defense for Kennedy, Robert McNamara.
When he left, however, the Strategic Air Command, which oversees most of the United States nuclear military strike force, changed the codes to 00000000. This extremely easy code was even written on a checklist, so no personnel would forget it.
The reasons were twofold. One, there would no need for presidential approval if there was an attack, and two, if the lines of communication had been destroyed, there would still be the ability to launch the missiles. Under the Strategic Air Command’s thinking, this ensured that launching nuclear missiles would be quick and easy.
A former Minuteman launch officer named Dr. Bruce Blair broke the news in an article in 2004 about what was once the very lax nuclear launch code. He had also written an article in 1977 warning that it could take just four people to launch a missile. This was the same year all the PALs were activated, and the codes were miraculously changed.
Sources: Today I Found Out, ArsTechnica, Huffington Post