Jennifer Lopez, 26, a saleswoman in Pembroke Pines, Fla., said: “There are cameras in stores and supermarkets. Our families would be safer and surveillance cameras would provide evidence to help agencies pursue people, like they just did in Boston.”

The nationwide poll of 965 adults was conducted on landlines and cellular phones from April 24 to April 28, five days after the manhunt for the surviving suspect in the Boston bombings, Dzhokhar Tsarnaev, ended with his capture in a backyard in Watertown, Mass. It has a margin of sampling error of plus or minus three percentage points.

Polls taken in the aftermath of terrorist attacks often show spikes in the public’s fears of another attack. In a CBS News poll a year ago, just 10 percent of people said another attack in the United States in the next few months was “very likely,” while 27 percent said it was “somewhat likely.” In the most recent survey, 24 percent said it was very likely and 42 percent somewhat likely.

There is also evidence that fears about immigrants have increased modestly. Forty-nine percent said the risk of terrorism had risen in the United States because of legal immigration. The last time that question was asked, in 2007, the percentage was 42 percent.

Still, other responses were unchanged since the Boston bombings: Twenty-three percent said they were very concerned about a terrorist attack in the area in which they live, about the same as said so in 2010. Fifty-six percent said they approved of Mr. Obama’s handling of terrorism, essentially unchanged from a CBS News poll in February.

Mr. Obama said the law enforcement system had functioned as it should in the days after the bombings. He also said the F.B.I. had properly handled the information it received from Russian intelligence agencies about the older of the two suspects, Tamerlan Tsarnaev, even as Mr. Obama conceded the difficulty of preventing attacks. “People, I think, understand that we’ve got to do everything we can to prevent these kinds of attacks from taking place,” Mr. Obama said. But he added, “We’re not going to stop living our lives because warped, twisted individuals try to intimidate us.”

Underscoring the president’s point, a large majority of those polled, 72 percent, said they did not plan to avoid large public events to reduce their exposure to potential terrorist attacks. That confidence came even as people were divided about whether their state and local authorities were prepared to deal with such an attack (48 percent said they were prepared; 41 percent said they were not).