Security experts have warned that cybercriminals have taken advantage of a security freeze in place in many parts of the world to access sensitive data.

In the case of Russia, the freezing means that the country has closed all major Internet sites and social media platforms.

It’s not clear what kind of data was affected by the cyberattack, but Russian security services have denied any responsibility for the breach.

In a statement released Friday, Russian cybersecurity firm Kaspersky Lab said it has identified more than 6,000 domains used to access the vulnerable software.

The firm said it will be working to find the other 1,200 vulnerable domains.

Russian President Vladimir Putin has blamed the cyberattacks on a new class of hackers called Distributed Denial of Service (DDOS) attackers.

The threat has been a persistent theme in Russian politics and business for years.

Last month, Putin accused the U.S. and Israel of orchestrating a “sophisticated” cyberattack against the country.

“The most important thing is that the government and the authorities of the Russian Federation take measures to protect the interests of the people, especially against a malicious attack,” Putin said.

“As a matter of fact, there are already many measures in place, like an agreement between the governments of the United States and the European Union, and also the cooperation of all the countries involved.”

Russian President Putin attends a news conference at the Kremlin in Moscow, Russia, October 19, 2017.AP