Internet traffic in Bahrain, the Persian Gulf kingdom, has declined by about 20%, likely as a result of more aggressive government filtering, a Web security company said.

According to Arbor Networks, a Chelmsford, Mass. supplier of anti-DoS (denial-of-service) technology, the amount of data going into and out of Bahrain is down approximately 20% this week compared to the traffic of the previous three weeks.

Arbor's traffic analysis was compiled using data from its ATLAS (Active Threat Level Analysis System) network, which collects Internet traffic information from approximately 120 carriers and providers worldwide.

"Data from 100 Internet providers around the world suggests Bahrain has significantly increased its filtering of Internet traffic in response to growing political unrest," said Arbor Networks. Craig Labovitz, Arbor's chief scientist, said it was impossible to tell what Bahrain was filtering or blocking. "We just have measurements that strongly suggest some form of traffic manipulation," Labovitz said in an e-mail .

Unlike in Egypt late last month, Bahrain's Internet infrastructure has remained online, Computer World reported.