Twenty-one of the world's 25 leading news organizations have been the target of likely government-sponsored hacking attacks, according to research by two Google security engineers.

While many Internet users face attacks via email designed to steal personal data, journalists are "massively overrepresented" among such targets, said Shane Huntley, a security software engineer at Google.

The attacks are launched by hackers working for or in support of a government, and specifically target journalists, Huntley and co-author Morgan Marquis-Boire said in interviews. Their paper was presented at a Black Hat conference of hackers in Singapore on Friday.