Security is the issue at hand when watching pornography on a smartphone, CNN reports.

A web-security company reported that nearly a quarter of malware on mobile devices comes from pornographic websites. The study is from Blue Coat, a web security and optimization firm, that reported that watching porn on a PC is safer than doing it on a smartphone.

Part of the problem, Blue Coat said, is that the nature of mobile devices makes differentiating legitimate sites from malicious ones a tricky task. There is no way to hover over shortened URLs to reveal their true destination, for example.