By John Letzing, MarketWatch

SAN FRANCISCO (MarketWatch) - Assistant Senate Majority Leader Dick Durbin (D-IL) said Tuesday he plans to hold a hearing next month to examine U.S. companies' business practices in "Internet-restricting countries."

Durbin's announcement comes shortly after Google Inc.'s decision to reevaluate its operations in China, after suffering a cyber-attack it said was aimed at exposing the identities of advocates for democratic reform there.

Durbin, the Chairman of the Judiciary Subcommittee on Human Rights and the Law, said he plans to examine whether other U.S. firms will follow Google's /quotes/comstock/15*!goog/quotes/nls/goog (GOOG 531.00, -0.12, -0.02%) example "in standing up to the Chinese government's continued failure to respect the fundamental human rights of free expression and privacy."

Durbin said he has sent letters to 30 companies, including Amazon.com Inc. /quotes/comstock/15*!amzn/quotes/nls/amzn (AMZN 118.02, -0.10, -0.09%) , Apple Inc. /quotes/comstock/15*!aapl/quotes/nls/aapl (AAPL 195.61, -0.25, -0.13%) and Facebook Inc., "seeking information about their human rights practices in China."

Google has said that following the cyber-attack, it's now reconsidering its approach to competing in China, and no longer wants to voluntarily censor its local search results on Google.cn.

"Google sets a strong example in standing up to the Chinese government's continued failure to respect the fundamental human rights of free expression and privacy," Durbin said in a statement. "I look forward to learning more about whether other American companies are willing to follow Google's lead."

In a letter addressed to Amazon.com Chief Executive Jeff Bezos, Durbin asks the CEO to detail the company's operations in China, and its "future plans for protecting human rights, including freedom of expression and privacy, in China."

Washington, D.C. lawmakers have long taken an interest in the business practices of U.S. Internet companies in countries seen as politically repressive.

In 2007, then-Yahoo Inc. /quotes/comstock/15*!yhoo/quotes/nls/yhoo (YHOO 15.19, +0.02, +0.13%) CEO Jerry Yang was grilled by the U.S. House Foreign Affairs Committee about the company's involvement in the detainment and torture of pro-democracy advocates in China.

In addition, legislation has been proposed on Capitol Hill that would establish a U.S. "Office of Global Internet Freedom," and require U.S. companies operating in China to report any requests by Chinese authorities for user information. See related story about the Global Online Freedom Act.

John Letzing is a MarketWatch reporter based in San Francisco.