The Ukrainian Hacker Group claimed to have attacked the Russian domain name registrar reg.ru. Cyber volunteers reported this on their Telegram channel.
They claim to have stolen data from a portion of the hosting provider's four-million-strong client base. They also published a "sample of five hundred databases."
"And of course, we don't bid farewell. Reg.ru can, for now, calmly change all passwords within an hour or two, inform users that their data is in Ukraine, and notify the regulator and counterintelligence," the hackers wrote.
What is known about reg.ru: It is the largest accredited domain name registrar and hosting provider in Russia. The provider serves 3.7 million clients, including Mail.ru, Avito, Auchan, "Alfa-Bank," Tilda, and "Electronic Moscow."