Unknown HZ value! (##) Assume 100 -- You've been hacked!On RHEL or Centos 4 or 5, If you run the linux command top and you see something like:
"Unknown HZ value! (75) Assume 100"
Yours might not say "75" -- it could be any number.
If you see this, you should run rkhunter immediately, because your box has probably been taken over by a rootkit -- either SHV4 or SHV5.
The only reason you see this clue "Unknown HZ value" is because the rootkit replaces the top command (among others) with a substitute top command that will hide its processes. Their replacement top is old (version 1.2) and cannot handle the HZ value of the 2.6 linux kernel.
Sad to say, but if this happens to you, its time to reinstall your OS!