L in u X ba sics for h acke rs g e t t I n g s t a r t e d w I t h

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Chapter 5
Summary
Linux’s use of permissions to protect a user’s or group’s files and directories 
from other users in the system can be used for offensive and defensive pur-
poses. You should now know how to manage these permissions and how to 
exploit weak points in this security system—in particular, 
SUID
and 
SGID
bits.
E XERCISES
Before you move on to Chapter 6, put the knowledge you learned from this 
chapter to the test by completing the following exercises:
1. Select a directory and run a long listing on it. Note the permissions on the 
files and directories.
2. Select a file you don’t have permission to execute and give yourself execute 
permissions using the chmod command. Try using both the numeral method 
(777) and the UGO method.
3. Choose another file and change its ownership using chown.
4. Use the find command to find all files with the SGID bit set.

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6
P R O C E S S M A N A G E M E N T
At any given time, a Linux system typically 
has hundreds, or sometimes even thousands, 
of processes running simultaneously. A process 
is simply a program that’s running and using 
resources. Examples of a process include a terminal, 
web server, any running commands, any databases, the 
GUI interface, and much more. Any good Linux administrator—and par­
ticularly a hacker—needs to under stand how to manage their processes to 
optimize their systems. For example, once a hacker takes control of a target 
system, they might want to find and stop a certain process, like an antivirus 
application or firewall. To do so, the hacker would first need to know how to 
find the process. The hacker might also want to set a scanning script to run 
periodically to find vul nerable systems, so we’ll also look at how to schedule 
such a script.
In this chapter, you’ll learn to manage those processes. First, you’ll 
learn to view and find processes and how to discover which processes 
are using the most resources. Then, you’ll learn to manage processes by 

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Chapter 6
running them in the background, prioritizing them, and killing them if 
necessary (no blood involved). Finally, you’ll learn to schedule processes to 
run on specified days and dates and at specific times.