Cybercriminals rely on blackhat SEO tactics to "poison" and manipulate search engine results to make links appear higher than legitimate ones, according to Patrik Runald. Links infected with malware and Trojans can appear near the top of the search results, generating a greater number of clicks to malicious Web sites.
This trend is becoming more common. The average number of malicious sites in Google searches using Google trending topics in 2009 rose to 13.7% for the top 100 results, Runald writes. This means for every 100 results, around 14 of the suggested links may link to a malicious site rather than the site the searcher wanted.