The cyberattacks Thursday and Friday on Twitter and other popular Web services disrupted the lives of hundreds of millions of Internet users, but the principal target appeared to be one man: a 34-year-old economics professor from the republic of Georgia.

During the assault  the latest eruption in a yearlong skirmish between nationalistic hackers in Russia and Georgia  unidentified attackers sent millions of spam e-mail messages and bombarded Twitter, Facebook and other services with junk messages. The blitz was an attempt to block the professor’s Web pages, where he was revisiting the events leading up to the brief territorial war between Russia and Georgia that began a year ago.

The attacks were “the equivalent of bombing a TV station because you don’t like one of the newscasters,” Mikko Hyppönen, chief research officer of the Internet security firm F-Secure, said in a blog post. “The amount of collateral damage is huge. Millions of users of Twitter, LiveJournal and Facebook have been experiencing problems because of this attack.”

The blogger, a refugee from the Abkhazia region, a territory on the Black Sea disputed between Russia and Georgia, writes under the name Cyxymu, but identified himself only by the name Giorgi in a telephone interview. Giorgi, who said he taught at Sukhumi State University, first noticed Thursday afternoon that LiveJournal, a popular blogging platform, was not working for him. “I decided to go to Facebook,” he said. “And Facebook didn’t work. Then I went to Twitter, and Twitter didn’t work. ‘How strange,’ I thought, ‘What a coincidence they all don’t work at once.’ ”