The hacking group Anonymous has disabled several Russian government websites including the state-run Russia Today News (RT.com).
A "distributed denial-of-service attack" technically known as DDoS flooded the news site with malicious traffic, blocking access for at least several hours.
This is the first attack in an expected wave of "cyber activity" against the Russian government.
Hackers uniting with the Anonymous group announced that they launched cyber operations that briefly took down the "Russia Today" website, as well as the sites of the Kremlin, the Russian government and the Russian Ministry of Defense websites.
Russia Today confirmed the attack, saying it slowed down some websites, while keeping others offline for "extended periods of time".
Russia Today's coverage of the situation in Ukraine was mostly pro-Russian, as it displayed fireworks and cheerful celebrations in Ukraine showing the people welcoming the Russian army.
In the UK, MPs have said the TV channel is the "personal propaganda tool" of Russian President Vladimir Putin and should be banned.
DoS attacks flood websites with traffic
Internet security expert Robert Potter said that the DDoS attack used;
Multiple systems aggressively targeting a site with massive requests for service, crippling other traffic accessing the service.
"It's like trying to push 5 people through a door at the same time," he added.
DDoS attacks are easy, and defense against them is easy.
One simple measure is to turn off foreign traffic to a website, which may explain why RT is easier to access from within Russia at the moment than abroad.
"De Dos is seldom effective in influence," Potter said.
"If you hit Amazon with D-Dos, they lose millions per minute, but for the news site of the Russian propaganda agency, it's not that important," he said.
But Potter says we are likely to see more anonymous "cyber activity".
Russia may "consider" a devastating cyber attack against the United States if NATO intervenes to defend Ukraine (Al-Jazeera)
Anonymous.. Has the group entered Russia's war on Ukraine?
Anonymous is a decentralized group without a hierarchy or leadership, and is known to deal with a wide range of political and social issues, having had a role in previous attacks targeting the CIA and the Islamic State in Iraq.
"There is a real danger of a state-to-state cyberwar, leading to a global escalation," Potter said.
The escalation includes the possibility of a Russian cyber attack on the United States.
In January, a US government intelligence briefing warned that Russia would "consider" a devastating cyber attack against the United States if NATO intervened to defend Ukraine.
Security experts have also warned that criminal gangs linked to Russia could be encouraged to target Australia with cyber attacks.
Earlier this week, Russian cyber forces launched DDoS attacks on the websites of several Ukrainian banks and government departments.
The government of Ukraine has asked volunteer "secret hackers" to help protect critical infrastructure and spy on Russian forces.