Calling for a "transparent" investigation, she added: "Countries that restrict free access to information or violate the basic rights of internet users risk walling themselves off from the progress of the next century."
Clinton cited China among several countries restricting the "free flow of information" or censoring the internet.
Among other countries she named were North Korea, Tunisia and Uzbekistan as well as Vietnam where she noted that access to social networking sites has "suddenly disappeared".
Google announced its surprise change of policy in China last week, saying that after uncovering the alleged attacks it would stop filtering its search results as required under Chinese censorship laws.
|Clinton said those behind cyber attacks must face serious consequences [AFP]
As a result, the company said, it may have to pull out of China and shut down its operations there.
The announcement marked an abrupt about-turn by Google, which first entered the Chinese market in 2006 saying it would adhere to Chinese internet censorship rules.
On Thursday Eric Schmidt, Google's chief executive, clarified the company's plans saying that the search giant was still censoring results in China but that would change soon.
"Our business in China is today unchanged. We continue to follow their laws, we continue to offer censored results. But in a reasonably short time from now we will be making some changes there," he told reporters.
The company has said it no longer wants to censor its Chinese Google.cn site and wants to talk with Chinese officials about offering a legal, unfiltered Chinese site.
China has so far given no indication it is open to that idea, warning earlier this week that all companies operating in the country would have to follow Chinese laws.1
A foreign ministry spokesman told reporters earlier this week that Google would be no exception.
"If Google has any problems in its business in China, these must be resolved according to Chinese law"
Chinese vice foreign minister
However, Chinese officials have also moved to downplay any impact of the Google dispute on broader trade and diplomatic ties with the US.
"The Google case should not be linked with relations between the two governments and countries," He Yafei, the Chinese vice foreign minister said.
"If Google has any problems in its business in China, these must be resolved according to Chinese law, and the Chinese government is willing to help resolve these problems."
In her speech on Thursday Clinton meanwhile reiterated the US stance that "no company should accept censorship".
"This issue is about more than claiming the moral high ground - it really comes down to the trust between firms and their customers," she said.
"Censorship should not be in any way accepted by any company from anywhere. And in America, American companies need to make a principled stand. I am confident that consumers worldwide will reward companies that follow those principles."