Some servers
"invisible" allow governments to intercept and modify online communications quietly of its citizens.
Google launched new charges against China this week, claiming that the country has interfered with access to some of its citizens to serve the Internet giant's Gmail, disguising interference and technical problems .
Security experts say it is very likely that China possesses invisible proxy servers, or "transparent proxies" to intercept and relay messages network rapidly altering the contents of those communications. This makes it possible to block emails and make it look like Gmail does not work correctly.
companies regularly use transparent proxies to filter the access of workers to the Internet. Some Internet providers have also used the technique to replace standard web ads with their own. But it is increasingly common for governments to use transparent proxies to censor and control the dissidents and protesters. All traffic from a given network is forced to pass through the proxy, which allows communications to be monitored and modified on the fly. Intercept and relay traffic attack is known as "man intermediary.
"What is done is to rewrite the content to be delivered to the user," says Nicholas J. Percoco, director of SpiderLabs , part of the security firm Trustwave. Percoco said the China ISP could track down anyone who use Gmail. To do this, "inject a keystroke logger JavaScript, which would record every keystroke that was done in the service."
defenses against attack are slim, especially if the Internet service provider has a valid certificate of encryption that all major national ISPs should have. By using a protocol known as HTTPS can prevent a middle man attack, and which encrypts information in transit. However, Microsoft said in a security advisory issued today that it had detected fraudulent certificates nine popular websites, including Google Mail, Microsoft's Live service, and Yahoo services. These fake certificates could also be used to intercept encrypted communications.
is believed that the Chinese government has tightened communications in response to political instability in the Middle East. Google found that problems with Gmail from within China came in the form of an attack that made the web application freezes when a user performs certain actions such as clicking the "send" button.
"There is no technical problem on our part, we have extensively tested," said a Google spokesman said in a statement by e-mail. "This is a government obstruction carefully designed so that it appears the problem is Gmail."
The attack appears to block the site only sporadically, stopping the web application access for a few minutes and then allowing the user to connect back to Gmail, Google explains.
Other nations have used intermediaries man tactics to interfere with Internet traffic. Tunisia adopted a similar approach by grabbing Facebook logins to watch over its citizens after widespread protests against the reign of Zine El Abidine Ben Ali. The protests were followed by mass riots in other countries like Yemen and the next door neighbor of Tunisia, Libya.
Facebook has become an important communications hub for the protesters in many countries. The Tunisian government was "using the transparent proxy to hijack the session of user accounts and then posting positive things about the government in the accounts of people on Facebook," said Percoco.
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