In January 2004, Pakistani scientist Abdul Qadeer Khan confessed to being the ringleader of a clandestine nuclear proliferation network that provided sensitive uranium enrichment technology to Libya, Iran and North Korea. Khan’s admission was the result of a decade of surveillance by American and British intelligence, though these agencies stopped short of claiming that Khan’s network provided actual designs for nuclear weapons to rogue states. After the dissolution of the Khan network, the Central Intelligence Agency and Secret Intelligence Service continued to investigate leads while the Pakistani government placed Khan under house arrest and declared “the A. Q. Khan affair to be over.”

Not quite. The story of the Khan network took a sinister turn this week when David Albright, a prominent expert on nuclear weapons, published a report saying that designs for an advanced, compact nuclear warhead were found on computers owned by Swiss businessmen who were members of Khan’s smuggling ring. “To many of these countries, it’s all about size and weight,” Albright said in an interview. “They need to be able to fit the device on the missiles they have.” The warhead depicted in the blueprints is of Pakistani origin and is small enough that it could easily be mounted on a medium-range ballistic missile.

U.S. intelligence officials, along with the UN’s nuclear “watchdog,” the IAEA, oversaw the destruction of more than a terabyte of seized data, including the blueprints in question. However, none of the Western intelligence services have any idea how many times the digital blueprints were copied and distributed. If Iran or North Korea received copies of the design, there is no question that their nuclear weapons programs have made a giant leap in a very short period of time. Just a month ago, nuclear proliferation experts were taking comfort in the fact that Iran would not be able to design a nuclear warhead small enough to fit on its Shahab III ballistic missile anytime in the near future. That assumption has been obliterated by the latest revelations about the Khan network.

Of course, the CIA will not comment on the report, citing ongoing national security issues, but former CIA director George Tenet acknowledged in 2007 that the agency had sources in the Khan network for at least a decade.