Nearly half of U.S. computer users online say they did not know that their choice of browser affects internet security, and few switch browsers even when they know the risk, according to a Norwegian study released Monday, reports the Associated Press. The survey of 2,835 of U.S. online users by Oslo-based browser-maker Opera Software found that only 51 percent was aware that a browser can affect a computer's vulnerability to viruses and spyware. Only 11 percent of respondents said they had switched browsers for security reasons. However, 66 percent said they would consider a change if it would improve security. The survey was conducted March 25-29 by Harris Interactive. Opera's browser market share is less than 0.2 percent.