The Pew Internet & American Life Project also found the attacks prompted more people to publish on the Web and get in contact with long-lost friends and relatives via e-mail.
"For tens of millions of Americans, the Internet became a channel for anguished and prayerful gatherings, for heartfelt communication through e-mail, and for vital information," researchers said.
The study found that the attacks had a profound effect on people's opinions about public information posted on the Web, even among those who generally favor disclosure.
A full 69 percent of people surveyed said it is OK for the government to remove information the public wants or needs in the interest of keeping it out of terrorists' hands. However, only 49 percent of survey respondents think the move will actually help in the fight against terrorism.
Of those who think the government should post information about chemicals or chemical plants, 60 percent said it should be taken down if it could help aid terrorists.
People are more divided when it comes to government monitoring of people's e-mail and Web habits. Just 45 percent think the government should have the right to monitor such communications, while 47 percent think it should not.
The attacks also altered how people and organizations use the Web to get and disseminate information. In the year following Sept. 11, people sent more e-mail, used more online news sites, and gave more donations online. According to the study, 19 million Americans used e-mail to rekindle relationships with friends and family after the attacks.
The attacks also spawned a surge in what the survey calls "do-it-yourself journalism."
"In the days after the attacks, the Web provided a broad catalog of facts and fancy related to Sept. 11, ranging from eyewitness accounts from New York, Washington and across the nation, to government reports, to analysis from experts and amateurs," the study said.