Washington: The National Aeronautics and Space Administration (Nasa) said hackers stole employee credentials and gained access to mission-critical projects last year in 13 major network breaches that could compromise US national security.

Nasa administration inspector-general Paul Martin testified before Congress last week on the breaches, which appear to be among the more significant in a string of security problems for federal agencies.

The space agency discovered in November that hackers working through an internet protocol address in China broke into the network of Nasa's Jet Propulsion Laboratory (JPL), Martin said in testimony released on Wednesday. The JPL manages 23 spacecraft conducting active space missions, including missions to Jupiter, Mars and Saturn was among those badly hit.

Denial

In a separate development, the US air force said on Friday it had scrapped a plan to outfit thousands of personnel with second-generation iPad tablet computers from Apple, but denied the reversal was because some of the software had been written in Russia.

The military and other branches of government have been putting an increased emphasis on ‘supply-chain security' as they try to make sure components have not been tampered with by other nations.

Mike Jacobs, who headed the National Security Agency's programme for defending US equipment, said in an interview he had killed a major procurement of encryption software within seconds after learning that a US supplier had included a small amount of Russian-made code.