NEW DELHI: Despite vast surveillance operations, governments will not be able to detect every suspicious interaction that takes place on phone and Internet networks, experts have said. By using encryption software that is readily available off the shelf, citizens can make it very difficult for government agencies to snoop in on their phone conversations or even messages exchanged over the Internet.

So, electronic surveillance programmes, such as the US government's PRISM—through which it clandestinely keeps a tab on people around the world by gathering data from several corporations—and India's Central Monitoring System, can do very little if users are determined to go off the radar.

"The point is not how easy the surveillance is to bypass; the point is how easy is it to evade notice even though everyone is being monitored all the time. And the answer is: very easy," said Bruce Schneier, a security technologist and author of Liars and Outliers, a book about security in the information society. Concerns about governments invading into the privacy of its citizens have come to the fore after classified documents about the PRISM programme were leaked to the media on June 6 by Edward Snowden, a former American intelligence officer and technical contractor.