Malware authors have used Search Engine Optimization (SEO) techniques to mix rogue search results in with legitimate results. For example, one of the rogue links is directly under a MSDN blog entry discussing Microsoft Security Essentials. The rogue redirects are hosted on compromised Web sites, including a Canadian publisher's Web site and the British Travel Health Association.
When a user browses to the compromised Web sites, so long as they have been referred by a search engine, they are redirected to malicious Web sites with domain names such as computer-scanner21 and computervirusscanner31.
More: Microsoft Security Essentials SEO Poisoning - Security Labs Alert