Social media websites Twitter and Facebook were the victims of a distributed denial-of-service (DDoS) attack yesterday afternoon, which took the services offline for an extended period of time.
Search engine Google was also affected by the internet assault, which is thought to have been targeted against one individual blogger known as Cyxymu.
The blogger is an outspoken critic of last year's conflict between Russia and Georgia, and harbours a number of controversial opinions.
All sites are now running as usual today, but an online audience of millions was disrupted by the problems.
Max Kelly, chief security officer at Facebook, explained to CNET News: "It was a simultaneous attack across a number of properties targeting him to keep his voice from being heard."
He added that an investigation has started into the source of the attacks and any individuals found guilty will have action taken against them.
The three sites affected recently appeared in market research firm comScore's list of June's most popular portals.
Google attracted a greater number of visitors than any other site in the world during the course of the month, while Facebook achieved its highest ranking yet (sixth) and Twitter entered the top 50 for the first time.
