The hacker who claimed responsibility for the cyber attack said it was to protest the killing of dolphins in Taiji, Japan. Government websites have been targeted before over Japan's controversial practice of whaling.
A hacker affiliated with the loosely-knit hacktivist movement Anonymous on Wednesday claimed responsibility for taking down several Japanese websites to protest dolphin hunting.
"The attack is protest against the dolphin killing in the cove of Taiji," the hacker wrote in a tweet, referring to a city in Japan where they trap dolphins in a cove and slaughter them. "Stop the killing of dolphins," the hacker said in another tweet.
The targeted websites included Japan's official National Tax Agency, independent government agency Japan External Trade Organization, and the private Japan Securities Finance Co.
On February 6, the same hacker claimed to have brought down the websites of three supermarkets and four restaurants in Iceland for supplying whale meat to consumers.
The hacker was also credited with bringing Japanese Prime Minister Shinzo Abe's website down in December. Chief Cabinet Secretary Yoshihide Suga said police were investigating the matter, reported The Japan Times, the country's largest English-language newspaper.
In November, a video posted online displayed a person in a Guy Fawkes mask - a symbol widely used by the Anonymous movement - threatening cyber attacks against Iceland and Japan if they did not stop killing whales and dolphins.
"Japan, you will be wise to listen and pay heed. You have blood on your hands and smiles on your faces," said the person in the video. "Make no mistake. Profiting from these creatures is a crime we will avenge."
Several other government agencies and organizations have reported cyber attacks claimed by Anonymous, including the Japan Association of Zoos and Aquariums, the Metropolitan Police Department and Narita International Airport, according to The Japan Times.
Japan continues to hunt whales and dolphins, citing research purposes despite a UN-backed international moratorium on the practice.