Charles Burton, a professor of Chinese politics at Brock University in St. Catharines, Ontario, told CBC News the hacking of Defense Research and Development Canada reflects Beijing's interest in NATO weaponry.
"Canada has access to secrets that are shared with other Western industrial countries, such as the United States, with regard to sophisticated weaponry. And the Chinese government would have strong interest in getting hold of technologies," he said.
China has denied any responsibility for the attacks.
The Finance Department and the Treasury Board also were targeted and that could be related to international pressure on China to revalue its currency, Burton said.
"With regard to the Treasury Board, the hackers would be able to get information about the passwords of key government officials that would then give them access to a wide range of classified data," Burton said.
Hackers also have struck oil and gas companies, a sector of great interest to China.