More than 25 billion online digital attacks on the Japanese government and other bodies were logged in 2014, an agency has said, with 40 percent of them traced to China.
The National Institute of Information and Communications Technology (NICT), which has a network of a quarter of a million sensors, said there were 25.66 billion attempts to compromise systems, according to a report by Kyodo News.
The figure includes attacks aimed at testing the vulnerability of software used in servers.
The survey was first carried out in 2005, when it recorded just 310 million attempts to breach security.
NICT said an increasing number of attacks involve attempts to take over routers, security cameras, and other systems connected to the internet.
Of the online attacks the agency was able to trace, 40 percent originated in China, while South Korea, Russia, and the US also figured prominently.
Compromised internet security is an increasing risk for firms around the world and in all sectors.
A Russian report released on Monday said online attacks since 2013 have cost banks around the globe up to $1 billion.
Sony Pictures was the victim of an online attack last year in which embarrassing emails were leaked to the press in an incident that US authorities blamed on North Korea. Pyongyang was incensed over The Interview, a film about a plot to assassinate the country's leader, Kim Jong-Un.