WASHINGTON -- Fighting homegrown terrorism by monitoring Internet communications is a civil liberties trade-off the U.S. government must make to beef up national security, the nation's homeland security chief said Friday.

As terrorists increasingly recruit U.S. citizens, the government needs to constantly balance Americans' civil rights and privacy with the need to keep people safe, said Homeland Security Secretary Janet Napolitano.

But finding that balance has become more complex as homegrown terrorists have used the Internet to reach out to extremists abroad for inspiration and training. Those contacts have spurred a recent rash of U.S.-based terror plots and incidents.

"The First Amendment protects radical opinions, but we need the legal tools to do things like monitor the recruitment of terrorists via the Internet," Napolitano told a gathering of the American Constitution Society for Law and Policy.

Napolitano's comments suggest an effort by the Obama administration to reach out to its more liberal, Democratic constituencies to assuage fears that terrorist worries will lead to the erosion of civil rights.

The administration has faced a number of civil liberties and privacy challenges in recent months as it has tried to increase airport security by adding full-body scanners, or track suspected terrorists traveling into the United States from other countries.

"Her speech is sign of the maturing of the administration on this issue," said Stewart Baker, former undersecretary for policy with the Department of Homeland Security. "They now appreciate the risks and the trade-offs much more clearly than when they first arrived, and to their credit, they've adjusted their preconceptions."

Underscoring her comments are a number of recent terror attacks over the past year where legal U.S. residents such as Times Square bombing suspect Faisal Shahzad and accused Fort Hood, Texas, shooter Maj. Nidal Hasan, are believed to have been inspired by the Internet postings of violent Islamic extremists.

And the fact that these are U.S. citizens or legal residents raises many legal and constitutional questions.

Napolitano said it is wrong to believe that if security is embraced, liberty is sacrificed.

She added, "We can significantly advance security without having a deleterious impact on individual rights in most instances. At the same time, there are situations where trade-offs are inevitable."

As an example, she noted the struggle to use full-body scanners at airports caused worries that they would invade people's privacy.

The scanners are useful in identifying explosives or other nonmetal weapons that ordinary metal-detectors might miss -- such as the explosives that authorities said were successfully brought on board the Detroit-bound airliner on Christmas Day by Nigerian Umar Farouk Abdulmutallab. He is accused of trying to detonate a bomb hidden in his underwear, but the explosives failed, and only burned Abdulmutallab.

U.S. officials, said Napolitano, have worked to institute a number of restrictions on the scanners' use in order to minimize that. The scans cannot be saved or stored on the machines by the operator, and Transportation Security Agency workers can't have phones or cameras that could capture the scan when near the machine.