Yahoo, YouTube ads spreading viruses

The $US43 billion online-advertising industry built by companies such as Yahoo and Google is jeopardising consumer privacy and giving hackers an easy path to infect computers, a US congressional investigation has found.

Now, armed with a better understanding of the opaque mechanics of web ads, Senator Carl Levin and other lawmakers are asking whether stricter rules are needed to protect consumers, setting up a battle with companies that shaped the internet.