Accusations of cyber-attacks allegedly perpetrated by China have been floating around for years, but today, for the first time, the Pentagon is directly accusing the Chinese of trying to break into US defense computer networks.

The Pentagon presented its annual report on Chinese military developments to Congress, entitled "Military and Security Developments Involving the People's Republic of China 2013" [PDF], in which it cited serious concerns about China's cybersnooping, stating that the "skills required for these intrusions are similar to those necessary to conduct computer network attacks."

China immediately dismissed the report as groundless. A spokeswoman from the Chinese foreign ministry responded to the accusations, saying that the US defense department has repeatedly "made irresponsible comments about China's normal and justified defense buildup and hyped up the so-called China military threat."

Several cases of network breaches attributed to Chinese hackers have been reported in recent months, including high-profile attacks on The New York Times that they say lasted approximately four months.

The attacks on news agencies were largely perceived as political and targeted journalists who were running stories about Chinese government officials. In contrast, in this report The Pentagon is warning that China is persistently carrying out attacks on the US in an effort to extract information from "diplomatic, economic and defense industrial base sectors that support U.S. national defense programs."

The information culled from US defense networks is likely being used to bolster China's own defense industry, the report said. They also warn that China is not limiting their scope to just government targets, but also acquiring data and intellectual property from the private sector.

"China continues to leverage foreign investments, commercial joint ventures, academic exchanges, the experience of repatriated Chinese students and researchers, and state sponsored industrial and technical espionage to increase the level of technologies and expertise available to support military research, development, and acquisition," the report said.

Cyber-espionage and cyber-attacks are an increasingly prominent threat. Earlier this year it was revealed that the Pentagon was increasing its cyber-defense personnel fivefold, from roughly 900 to 4,900 over the next several years.