Overall, bots—good and bad—are responsible for 52 percent of web traffic, according to a new report by the security firm Imperva, which issues an annual assessment of bot activity online. The 52-percent stat is significant because it represents a tip of the scales since last year’s report, which found human traffic had overtaken bot traffic for the first time since at least 2012, when Imperva began tracking bot activity online. Now, the latest survey, which is based on an analysis of nearly 17 billion website visits from across 100,000 domains, shows bots are back on top. Not only that, but harmful bots have the edge over helper bots, which were responsible for 29 percent and 23 percent of all web traffic, respectively.

“The most alarming statistic in this report is also the most persistent trend it observes,” writes Igal Zeifman, Imperva’s marketing director, in a blog post about the research. “For the past five years, every third website visitor was an attack bot.”

Put another way: More than 94 percent of the 100,000 domains included in the report experienced at least one bot attack over the 90-day period in Imperva’s study.