"Q. Most rootkits use the power of the kernel to hide themselves, they are only visible from within the kernel. How do I detect rootkits under CentOS or Debian Linux server?
"A. A rootkit is a program (or combination of several programs) designed to take fundamental control (in Unix terms 'root' access, in Windows terms 'Administrator' access) of a computer system, without authorization by the system’s owners and legitimate managers..."
