Fully 9 out of 10 consumers say they have made at least one change to avoid unwanted software, the Pew Internet & American Life Project found. For example, more than 80 percent of the 2,000 adults surveyed by Pew said they had stopped opening email attachments unless they were sure the documents were safe.
Other behavioral changes included nearly half of the respondents no longer visiting websites that they feared might deliver unwanted programs. One in 4 said they had stopped downloading music or video files from peer-to-peer networks, and nearly 1 in 5 said they started using a different web browser to avoid software intrusions.
"Spyware has had a chilling effect," Susannah Fox, associate director of Pew, said.
The impact of spyware and viruses on behavior involves 10s of millions of Americans, the research firm said. Nearly 7 in 10 home Internet users, or about 93 million Americans, have experienced at least one problem associated with unwanted software.
Those problems include computers slowing down, freezing up, or crashing. In addition, some respondents reported seeing new programs appear that they didn't install, new icons suddenly appearing on the desktop, and having their Internet home page changed without them resetting it.
While 80 percent of consumers said they knew about spyware, only about half claimed to have a grasp of the concept of adware, which comes bundled with free software downloaded from the Internet.
Adware tracks a person's Internet habits, so the information can be used to provide targeted advertising on the person's computer. Spyware, on the other hand, is installed without explicit consent and can sometimes be used to track site visits and record keystrokes in order to try to steal passwords.
Even though legitimate marketers often use adware, consumers still don't like it, Fox said.
"They don't want to be followed around," she said. "Consumers are increasingly skeptical about tracking, and about downloading extra programs, such as adware, that go along with free software that people enjoy."
As a result, more consumer education is needed, if marketers hope to change opinions of adware, Fox said.