Pro-Ukrainian hacking group Blackjack has claimed to have breached a Moscow internet service provider in revenge for a Russian attack last month on Kyivstar, Ukraine’s largest telecom provider.

The cyberattack targeted Moscow-based M9 Telecom and is reported to have destroyed the provider’s servers, deleting about 20 terabytes of data, including the company’s official website, branch websites, mail server and cyber protection services.

According to the Kyiv Independent today, some Moscow residents were left without access to the internet and television. The hackers said the attack was a warmup for a larger cyberattack that would be “serious revenge for Kyivstar.”

Blackjack also reportedly stole more than 10 GB from M9 Telecom mail servers and client databases and has made them publicly available. The attack isn’t the first undertaken by the hacking group recently, with Blackjack reportedly having conducted a cyberattack against Russian water utility company Rosvodokanal in December.

The attack on Kyivstar last month resulted in a “large-scale technical failure” and widespread service disruption for the company’s 24 million customers. It’s not known how many customers were affected by the later revenge attack.

“The war began in cyberspace with Russia launching destructive cyberattacks on Jan 13, 2022, and it will escalate in cyberspace,” Tom Kellermann, senior vice president of Cyber Strategy at application security software provider Contrast Security Inc., told SiliconANGLE. “Ukraine’s cyberwarfare capabilities have improved dramatically due to advice from NATO. Russia is reaping what she sows. I expect many more destructive cyberattacks to be launched against both sides and the West this winter.”

James McQuiggan, security awareness advocate at security awareness training company KnowBe4 Inc., noted that the attack of M9 Telecon highlights the importance of continuous monitoring, threat hunting and robust cybersecurity hygiene to detect and mitigate such advanced persistent threats.

“The evolving landscape of cyber warfare, illustrated by these incidents, calls for reevaluating cybersecurity strategies,” McQuiggan added. “Organizations must consider the technical aspects and the geopolitical implications of cyberthreats.”

Image: DALL-E 3