Ukraine's military intelligence agency (HUR) was behind a large-scale DDoS attack that "paralyzed" the work of several Russian ministries and companies, a source in the agency told the Kyiv Independent on June 5.
Roskomnadzor, Russia's state communications regulator, said on June 3 that several government websites had been rendered "partially inaccessible," allegedly due to the failure of "sections of the main communications network."
The source told the Kyiv Independent that the failure was, in fact, caused by the cyberattack.
Ukrainska Pravda (UP) reported that according to its undisclosed military intelligence source, the attack is still ongoing.
Electronic services of the ministries of defense, finance, interior, justice, industry, digital development and communications, and emergency situations were inaccessible as of the morning of June 5, UP's source claimed.
The Russian Defense Ministry website appears available as of 1:30 p.m. June 5, Kyiv time, but a number of other government sites, including those of the Interior Ministry, the Justice Ministry, or the Finance Ministry, remain inaccessible at the time of the publication.
The cyberattack also targeted the website and other services of the Federal Tax Service, the source said. Russia's Federal Customs Service reported temporary "complications in information exchange with participants in foreign economic activities" after a "massive DDoS attack on telecommunication operators."
The issues also reportedly affected the United Aircraft Corporation, the Sberbank and Alfabank banks, the Vkontakte social network, as well as other services and companies.
Cyberattacks have become an increasingly common tool employed by both sides of the Russia-Ukraine war. In one of the most devastating strikes, Russian hackers targeted Ukraine's telecommunications provider, Kyivstar, causing communication outages nationwide last December.
In turn, Ukraine's military intelligence agency or Ukraine-affiliated hackers have carried out a number of cyberattacks against Russian companies and state institutions, sources in the agency previously told the Kyiv Independent.
Read also: SBU cybersecurity chief: Hackers had access to Kyivstar months before December attack