Americans are worried about being tracked -- both by the government and by online marketers.

A survey released Wednesday by the Pew Research Center found privacy concerns heightened amid revelations of government snooping and ongoing concerns about how online marketers use their data.

Among those surveyed 80 percent said they "agree" or "strongly agree" that Americans should be concerned about government monitoring of phone calls and Internet communications.

Some 43 percent said they heard "a lot" about government data monitoring and another 44 percent said they heard "a little" about it.

The survey also showed a lack of confidence about the security of communications channels and social media.

A total of 81 percent in the survey said they felt "not very" or "not at all secure" using social media sites to share private information and 68 percent said they felt insecure using chat or instant messages.

More than half said they were concerned about security of text messages and email, and nearly half expressed worries about mobile phone security. With landline phones however, just 31 percent said they felt insecure about sharing private information.

"Far from being apathetic about their privacy, most Americans say they want to do more to protect it," said Lee Rainie, director of the research center's Internet Project and a co-author of the study.

The survey found 91 percent of respondents believed consumers have lost control over how personal information is collected and used by companies, and 64 percent said the government should do more to regulate how marketers use personal information.

- Privacy tradeoffs -

Some of those surveyed said they were willing to accept tradeoffs of privacy for some kind of service: 55 percent said they were willing to share some information in order to use online services for free.

The survey comes more than a year after leaked documents showed a vast surveillance system led by the National Security Agency which could sweep up data from Americans as well as foreigners.

The revelations from former NSA contractor Edward Snowden led to a public outcry and strained relations with US allies.

"One of the most notable findings in the study is that those who have heard the most about government surveillance are more privacy-sensitive across an array of questions in the survey," said Pew researcher Mary Madden.

"Those who are more aware of the monitoring programs feel considerably less secure using any communications channel to share private information."

This report is the first in a series of studies of Americans' privacy perceptions and behaviors following the Snowden revelations in June 2013.

The researchers created a panel of 607 adults who agreed to respond to four surveys over the course of one year.

The first of the surveys was conducted between January 11 and 28, with an estimated margin of error of 3.98 percentage points.