TOKYO (Kyodo) -- At least 46 entities in Japan, including banks and government agencies, have been targeted by cyberattacks likely utilizing the same malware since the end of last year, a major internet security firm said Thursday.

According to Trend Micro Inc., Japan Airlines Co., NTT Docomo Inc. and major banks were among the victims of distributed denial-of-service, or DDoS, attacks in which networks are overwhelmed by data from multiple sources over a short period, causing temporary service suspensions.

The Japan Weather Association said on Thursday it was hit by a cyberattack that rendered its information website inaccessible for over nine hours from around 7 a.m.

A similar cyberattack on Sunday that affected both the web and app versions of the weather site took over 7 hours to resolve.

According to Trend Micro, the hackers are believed to have used a botnet, or a network of computers and other internet-connected devices infected by malware used to carry out the attacks.

Upon investigating the incident against JAL, Trend Micro uncovered instructions to attack the IP addresses of the affected entities through a specific botnet. There were also signs of similar assaults in the United States and Europe.

"We can't rule out the possibility that multiple groups conducted attacks at the same time," a Trend Micro official said.

The hackers were able to simultaneously control devices including cameras and home appliances connected to the internet to carry out the attacks, the security firm said.