This is related to viruses and malware and links to the study.
http://www.huffingtonpost.com/2010/0..._n_610486.html
X-rated content aside, are online porn sites safe to visit?
A study conducted by International Secure System Lab--one of the first to examine the security risks of browsing porn websites--suggests that "shady" practices and malware are common on many porn sites, which could potentially make visitors the targets of cybercriminals.
The researchers analyzed some 269,000 free and pay adult websites on 35,000 domains.