REUTERS/Kevin Lamarque

It turns out the folks who protect America from missile attacks for a living are surfing porn on the job.

The executive director of the Pentagon's Missile Defence Agency penned a memo to employees and contractors telling them steer clear of X-rated websites at work, reports Bloomberg News.

"Specifically, there have been instances of employees and contractors accessing websites, or transmitting messages, containing pornographic or sexually explicit images," John James Jr. reportedly wrote in the July 27 memo obtained by Bloomberg News.

But this behaviour does more than corrupt morals -- it can corrupt important Pentagon computer systems.

"These actions are not only unprofessional, they reflect time taken away from designated duties, are in clear violation of federal and (Department of Defence) and regulations, consume network resources and can compromise the security of the network though the introduction of malware or malicious code."

Asked for comment, agency spokesman Rick Lehner said the memo was prompted by "a few people downloading material from some websites that were known to have had virus and malware issues."