According to US authorities, North Korean hackers were responsible for the theft of cryptocurrencies worth hundreds of millions of euros last month.
The FBI said on Thursday that two hacking groups "affiliated" with North Korea called the Lazarus Group and APT38 were responsible for the digital heist in the online game Axie Infinity.
They stole cryptocurrencies worth around $620 million (€570 million) during the attack around two weeks ago.
It was one of the largest digital heists ever.
Notorious hackers
The Lazarus Group rose to prominence in 2014 when it was accused of hacking film production company Sony Pictures Entertainment in revenge for the satirical film The Interview.
The film satirizes North Korea's leader Kim Jong-un.
The North Korean hacking program dates back at least to the mid-1990s, according to a 2020 US military report.
North Korea now employs around 6,000 hackers who are said to be organized in a unit called Bureau 121.
They therefore operate from several countries, including Belarus, China, India, Malaysia and Russia.
North Korean hackers are said to have stolen around $400 million worth of cryptocurrencies through cyberattacks last year, data platform Chainalysis reported in January.
A lot of money in the game
In the game Axie Infinity, players take part in battles with colorful blob-like avatars.
These avatars are Non-Fungible Tokens (NFT), a type of unique digital artwork that can be sold, rented, and farmed.
According to the manufacturer, the game had 2.5 million daily active users before the attack.
The attackers targeted so-called bridge software that allowed users to exchange in-game rewards for cryptocurrency.
Among other things, 173,600 units of the digital currency Ethereum were stolen, said the operators of the hacked Ronin Bridge.
The attackers used hacked crypto keys.
Bridges have been considered a potential risk in the industry for some time, as little is known about their security measures.