Guatemala's ongoing political crisis, which began with the murder of lawyer Rodrigo Rosenberg and has been fueled largely by YouTube, Facebook, Twitter and blogs, reached a new level over the weekend when several ISPs began blocking access to WordPress.com. This is the first known case of widespread Internet filtering in the country.

The Internet and mobile phones have taken on a major role in Iranian politics over the last several months. As protests over the contested election results continue in Iran, the government has dramatically increased its control over digital technologies. Many important Web sites have been blocked over the past couple of days, including the Web sites of the opposition parties in Iran, Facebook, Twitter, and YouTube. While political organizers have learned to leverage the organizing power of Web 2.0 tools, government censors in Iran are quick to shut them down when they are most effective. None of this is surprising; it reflects similar events seen in many places around the world.

The OpenNet Initiative worked this week to evaluate the functionality of China's Green Dam software. In "China's Green Dam: The Implications of Government Control Encroaching on the Home PC," we review the functional elements of this new software and explore the possible effects of its implementation on a national scale. We conclude that Green Dam is deeply flawed and poses critical security concerns for users.

The latest news in the world of Internet censorship is about China's Green Dam software, which ostensibly protects Chinese children by filtering out pornographic Web sites. In addition to blocking sites that include keywords such as "pornography" and, somewhat less justifiably, "touch" and "play," the software also filters out images that have a high percentage of "skin colored" pixels.

In preparation for the 20th anniversary of the Tiananmen Square massacre on Thursday, China has blocked access to Twitter, Hotmail, Flickr, MSN Spaces and several other web services.