A cybersecurity firm has identified distributed denial of service, or DDoS, attacks targeting 46 companies and organizations in Japan.

Major Japanese companies including Japan Airlines, MUFG Bank and NTT Docomo were under cyberattack from late December. The businesses say this led to glitches in their systems or disrupted access to their websites.

The attacks are believed to be the DDos type, in which massive amounts of data are sent to websites or servers to make them crash.

Trend Micro has identified and analyzed networks called botnets that were highly likely used in the attacks.

The company has learned that 46 businesses and organizations in Japan came under such attacks between December 27 and January 9.

It says the targets included companies in brokerage, insurance, transport and other sectors, and had little in common. Companies in the United States and other countries were also targeted.

Okamoto Katsuyuki at Trend Micro says the attacks may have been part of the same campaign.

He says that while it's difficult to determine their purpose, they may have been carried out for surveillance in preparation for a full-fledged attack.