Iran activists work to elude crackdown on Internet: Via AP on Yahoo! News.

The tweets still fly and the videos hit YouTube whenever protesters take to the streets in Iran — even as the Internet battle there turns more grueling.

Authorities appear to be intensifying their campaign to block Web sites and chase down the opposition online, and the activists search for new ways to elude them.

Sites such as Facebook, Twitter and YouTube remain blocked, as they have been since Iran's political turmoil began following the disputed June 12 presidential election. Internet experts believe the government is going further — including tracking down computers from which images and videos of Iran's protests are sent out to the rest of the world. Activists fear their every move online is watched.

"We are really worried about this. To protect myself, I just limit my posts on social networks, my tweets and also I deleted some parts of my personal blogs and my other notes on the Web," one Iranian who regularly sends tweets about the election turmoil said in an e-mail to The Associated Press.

Another said, "Every site where people can gather and stay connected and share news and pics ... is blocked." Both agreed to e-mail interviews on condition of anonymity, fearing government retaliation.

The government is believed to have been aggressively developing software and technology in recent years to strengthen its filtering and monitoring of Web sites. Since the election, a number of Internet experts are countering by providing Iranians with improved proxy systems and other programs to get around government blocks and escape detection.

"I think the Iranian government is learning quickly how to control and contain these things," said Andrew Lewman, executive director of The Tor Project Inc., based in Boston.

His group's free downloadable Tor program allows Internet users to work through a network of relays run by volunteers around the world to access blocked sites and hide what they are doing on the Internet. Active sessions using Tor in Iran have jumped from a few hundred before the election to thousands after, the nonprofit group said.

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