The world's three fastest Internet access speeds are in the United States, in Berkeley and Stanford, Calif. and Chapel Hill, N.C., but Japan leads across the board, according to a report released Tuesday by Internet content accelerator Akamai.

In its State of the Internet report, Akamai found that 48 of the top 100 cities are in Japan and 62 are in Asia. Analyzing average connection speeds, Akamai found that 31 U.S. states increased their speeds in the fourth quarter, paced by an 18% gain in South Dakota whose rates jumped to 4.5 Mbps. Decreases were recorded in 19 states and the District of Columbia.

Leading the race to the bottom was Virginia, which had a 13% drop. Akamai said the Virginia decline was likely caused in part by increased mobile connections on the Internet there.

"Every quarter we measure cities by their average access speeds," said a company spokesman Tuesday. "We monitor 465 million unique IP connections and that number is growing every quarter."

Akamai said that the U.S. and China, combined, account for nearly 40% of the IP addresses it observed.

The top three countries, in order of highest access speed, were South Korea, Hong Kong (which was counted in the country rankings), and Japan. The three countries were the only ones to surpass 7.5 Mbps average connection speed.

On a global basis, Akamai found that 96 countries had average connection speeds below 1 Mbps, a drop from the 103 countries in the previous quarter, indicating there has been some progress in deploying higher speed connections. Just three countries had average connection speeds below 100 Kbps.

The company began tracking mobile connectivity in the most recent quarter and found a wide range in average measured connection speeds with an Austrian mobile provider delivering 3.2 Mbps and a Slovakian carrier delivering 106 Kbps average measured connection speeds.

Russia led in "attack traffic" with 13% of malicious attacks recorded by Akamai. In second place was the United States, followed by China.