Rootkits are still a security scanner’s worst nightmare: New rootkit detection tests recently conducted by AV-Test.org found that security suites and online Web scanners detected overall only a little more than half of rootkits.

AV-Test.org, an indie security test organization based in Germany, ran two rootkit tests last month, one on Microsoft’s XP Home Edition and another on Microsoft Vista Ultimate Edition, the results of which have been published in a paper now available on the group’s Website.