Several advertising networks have access to millions of smartphones globally, after they have been secretly collecting app users personal details over the past year, U.S.-based mobile security firm LookOut said.
These actions are rising up and some of the most advanced mobile viruses can even create charges to consumers phone bill or crash the devices.
"Aggressive ad networks are much more prevalent than malicious applications. It is the most prevalent mobile privacy issue that exists," said Kevin Mahaffey, LookOut's technology chief and co-founder.
According to the company, over 80 million apps were downloaded and can take data from the phone or install software without users' knowledge. Others can collect users email addresses or phone numbers without permission and install icons to home screens.
LookOut didn't give the name of the most aggressive ad networks, but Jules Polonetsky, co-chair of the American thinktank Future of Privacy Forum, said consumers need to be aware of the risks.
Advertising networks, which are the link between large numbers of advertisers, have seen a good opportunity on the success and huge audience of Google's Android platform to obtain revenue streams.
However, consumers are increasingly concerned on privacy issues and these worries may hurt those aggressive practices.
Experts say that mobile advertising are still very much derived from the web, “where practices have not been very respectful”, said Anne Bezancon, founder and president of Placecast.
"The mobile experience is much more intimate and personal. A phone is an extension of you, not a distant publishing screen”, she added.