Bot traffic was on the rise in 2013, with approximately 61.5 percent of all website traffic produced by "non-human entities," according to a report from Incapsula.

The good news is that 31 percent of that bot traffic is from legitimate sources, like search engines crawling the Web for content to index. Incidents of scrapers, hacking tools, and spammers did not see any huge jumps this year, but the "other impersonators" category - which includes those with malicious intent - was up 8 percent.

Altogether, about 31 percent of bots are still malicious, but there are much fewer spammers, with activity dropping from 2 percent last year to 0.5 percent in 2013.

"The most plausible explanation for this steep decrease is Google's anti-spam campaign, which includes the recent Penguin 2.0 and 2.1 updates," Incapsula said, referencing Google's bid to surface "high-quality" content on the Web. "SEO link building was always a major motivation for automated link spamming. With its latest Penguin updates Google managed to increase the perceivable risk for comment spamming SEO techniques, while also driving down their actual effectiveness."

Incapsula said Google was able to produce a 75 percent decrease in automated link-spamming activity.

Still, the firm found evidence of more sophisticated hacker activity, with about 20.5 percent of Web traffic originating from those who fell into the "other impersonators" category, an 8 percent jump.

This group "consists of unclassified bots with hostile intentions," Incapsula said. "The common denominator for this group is that all of its members are trying to assume someone else's identity," like a search engine bot. But "the goal is always the same - to infiltrate their way through the website's security measures."

In the bot hierarchy, these impersonators are often the queen bee, Incapsula said. "These can be automated spy bots, human-like DDoS agents or a Trojan-activated barebones browser," the firm said. "One way or another, these are also the tools of top-tier hackers who are proficient enough to create their own malware."

"The 8 percent increase in the number of such bots highlights the increased activity of such hackers, as well as the rise in targeted cyber attacks," Incapsula found. "This is also reflective of the latest trends in DDoS attacks, which are evolving from volumetric Layer 3-4 attacks to much more sophisticated and dangerous Layer 7 multi-vector threats."

Legitimate bot traffic, meanwhile, saw a 55 percent increase in 2013, which Incapsula attributed to the evolution of Web-based services and the increased activity of existing bots. Every time a new service comes online, it creates new bots, while Incapsula saw that existing bots are crawling at an increased rate "to allow higher sampling rates, which also results in additional bot traffic."