Most computer security analysts did not cite a specific source of the attack Thursday.

But Bill Woodcock, a research director of the Packet Clearing House, a nonprofit technical organization that tracks Internet traffic, said Thursday’s attack was an extension of the conflict between Russia and Georgia. It was not clear who initiated the attack, he said, but likely “one side put up propaganda, the other side figured this out and is attacking them.”

Instead of using a botnet, or a network of thousands of malware-infected personal computers to flood a site with traffic, Mr. Woodcock said this particular attack consisted of a wave of spam e-mail messages, which began infiltrating Twitter and other sites at 10:25 a.m. Eastern time. “It’s a vast increase in traffic that creates the denial-of-service,” he said.