"The standard techniques used for analysis such as the examination of checksum or tools such as "rkhunter" are therefore not able to track down the malicious code."

rkhunter is out of date.

http://rkhunter.sourceforge.net/

http://en.wikipedia.org/wiki/Rkhunter

We use it as well but I'm not sure it is an example of a serious security practice when given with only one other "checksum or tools such as" type statement.