The Pentagon is investigating a cyber breach of some of its travel records that led to personal information being exposed, the military said Friday.
Lieutenant Colonel Joseph Buccino, a Pentagon spokesman, said there had been a breach of some "personally identifiable information" when a "single commercial vendor" was hacked.
Buccino said the breach only affected a small percentage of personnel and the Pentagon was investigating the incident.
Military leadership was made aware of the breach on Oct. 4.
A federal government report earlier this week said the Pentagon had been slow to protect major weapon systems from cyberattacks and routinely found critical vulnerabilities that hackers could potentially exploit in those systems.
Cybersecurity has been receiving increasing attention among U.S military and intelligence officials.
Last week, Western countries issued coordinated denunciations of Russia for running what they described as a global hacking campaign, targeting institutions from sports anti-doping bodies to a nuclear power company and the chemical weapons watchdog.
In some of the strongest language aimed at Moscow since the Cold War, Britain said Russia had become a "pariah state."