Outage hits CNN.com

CNN.com experienced about four hours of intermittent site inaccessibility Monday afternoon, according to research firm Keynote Systems. At one point, only one in 10 visitors who tried to access the site got through. By 4 p.m. PDT, the site was back to normal. A software glitch, not a computer-based attack, is the likely culprit, according to Keynote.

According to Keynote spokesman Dan Todd, the trouble started at 12:15 p.m. PT. Just after 1 p.m., accessibility dropped to 13 percent, Todd said. The problem stemmed from a failure of CNN.com's domain name servers. Surfers who knew CNN.com's IP address were able to access the site throughout.

A source in CNN.com's technical department said her staff was unaware of any problems with the site at midday.

Todd said initial research showed discrepancies in software being used on CNN.com's various DNS servers, and his company believes that's the source of the problem. --Bob Sullivan, MSNBC