Wen Weiping, a professor with School of Software and Microelectronics of Peking University, said that it is difficult to trace the countless attackers' identities, let alone determine who their supporters are.

"Actually China is quite vulnerable to cyber attacks because of the limited cyber technology or security awareness," he said.

In response to questions about the size of its 2012 defense budget, Yang said China's military spending depends on its defense needs and development strategies.

China increased its defense budget by 11.2 percent to 670 billion yuan ($106 billion) in 2012 during the National People's Congress earlier this month.

The growth in military spending has aroused the attention of foreign countries.

The increase is mainly to fund efforts to raise the standard of living of service people amid inflation, upgrade outdated armaments and infrastructures, as well as to meet the soaring need to safeguard expanding overseas interests, Yang said.

While China's military spending amounted to 1.28 percent of its GDP in 2011, spending by the world's major military powers exceeded 2 percent, the spokesman said.

"China's defense budget is only one-sixth of that of the US this year," he said.

Yang added that China is transparent with its defense figures, refuting charges that the actual figure was underreported.

It's difficult for China to hide extra expenses since all of its military expenditures come from the state, which publishes the budget during the annual NPC meeting, said Pan Zheng, a researcher at the National Defense University.