WASHINGTON—Hosting the 2020 summer Olympic games makes Tokyo a target for cyberattacks, and the best defense is international cooperation, experts said Tuesday.

At last year’s games in South Korea, cyberattacks downed hundreds of computers, taking the Internet and TV systems offline for half a day.

The Washington Post reported that U.S. intelligence had identified Russia as the culprit, though the attack was made to look like North Korea had carried it out. Russia was blocked from competing in South Korea due to doping violations.

“These kinds of international events are ripe for bad actors like Russia to carry out cyberattacks, whether they’re testing new capabilities or whether they’re angry they’re prevented from participating,” said Meg King, a strategic and national security adviser at the Woodrow Wilson Center, where the expert panel was convened.

With upcoming Olympics games in Beijing, Paris and Los Angeles, Keio University professor Motohiro Tsuchiya said that the international community needed to coordinate defense strategies. The Japan Computer Emergency Response Team Coordination Center, for example, is a member of the global Forum of Incident Response and Security Teams, which helps resolve cyberattacks.

Motohiro Tsuchiya, professor of Media and Governance at Keio University, said that Olympic host countries are vulnerable to blackouts and hacks to transportation, the Internet, TV event streams and to personal information on hotel and ticket booking sites. 

Japan is directly testing its own population for weaknesses.

On Feb. 20, the government-backed National Institute of Information and Communications Technology began hacking over 200 million IP addresses connected to Japan, searching for poorly secured devices with common username and password combinations. Japan’s constitution prohibits tapping into personal communications, but in late January, the government approved an amendment allowing it to hack certain civilian devices.

The initiative eschews complex smartphones and instead tests the security of routers, webcams and other internet-enabled objects like smart home appliances.  This network of newly connected devices is called the “Internet of things,” and it’s highly insecure.

Major Internet of things attacks in 2016 led to the outages of popular websites like Twitter, Spotify and Netflix.

Tsuchiya said that while Japan’s actions are a “violation of secrecy of communication,” and many people are opposed to the policy, “we want to have a better, cleaner cyberspace.”

Some doubt the country’s leadership, however. Last November, Japan’s recentl -appointed cybersecurity and Olympics minister told the parliament he’d never used a computer before.

But i the International Olympic Committee controls systems in Olympic stadiums, not host countries. The committee created a commission to address cybersecurity after a confidential document relating to the Russian doping investigation was hacked. Japan will administer aspects such as ticketing, the press center and visitor Wi-Fi.

The country’s efforts to control what it can are part of its recognition of the long-term need for cybersecurity.

“The Olympic games [are] a good target, but [they’re] not an ultimate target,” said Tsuchiya. “We have to survive those Olympic games, to live after that. We have to prepare for the future.”