In response, Google has stepped up its game. One of the reasons it has been scouring the Web for malicious pages is so that it can identify drive-by-download sites and warn Google searchers before they visit them. Nowadays about 1.3 percent of all Google search queries list malicious results somewhere on the first few pages. It turns out the Web's nice neighborhoods aren't necessarily safer than its red-light districts.
"We looked into this and indeed we found that if you ended up going to adult-oriented pages, your risk of being exposed [to malicious software] was slightly higher," he said. But "there really wasn't a huge difference."