Every sysadmin will try its best to secure the system/s he is managing. Hopefully you never had to restore your own system from a compromise and you will not have to do this in the future. Working on several projects to restore a compromised Linux system for various clients, I have developed a set of rules that others might find useful in similar situations.
The type of hacks encountered can be very variate and you might see very different ones than the one I will present, or I have seen live, but even so, this rules might be used as a starting point to develop your own recovery plan.
In most cases if you have a system compromise at root level, you will hear that you have to fully reinstall the system and start fresh because it will be very hard to remove all the hidden files the attacker has placed on the system. This is completely true and if you can afford to do this then you should do it. Still even in this case the compromised system contains valuable information that can be used to understand the attack and prevent it in the future.Read Full Story