When we first gain access to a Linux box there is a good chance that we have gotten a low level account. The next step is usually to escalate our privileges (give us access to more than we have now) up so we can view things like the shadow file. Or maybe there are certain tool we want to run to attack another system and need to be root to run these tools.

I wanted to give some idea of commands we can run to get information that may help us to escalate our privileges and then give really basic example to show what I mean.

Who are you?
Linux Command: id

Where are you?
pwd

What version of Linux is running?
uname -a

What can you do?
sudo -l

Find all files and directories that are owned by you
find / -user `whoami` -ls 2> /dev/null

List (running) processes/cronjobs
ps aux
cat /etc/crontab
crontab -e
ls -R /etc/periodic/

List Listeners/Sockets/Open files in general
lsof -i
netstat -an

List users & groups
cat /etc/passwd
cat /etc/groups

Find SUID/SGID binaries
find / \( -perm -2000 -or -perm -4000 \) -ls 2> /dev/null

Find files that have been accessed/modified/changed recently (e.g. in past 60 Minutes)
find / -type f -amin 60 -ls 2> /dev/null
find / -type f -mmin 60 -ls 2> /dev/null
find / -type f -cmin 60 -ls 2> /dev/null

List files in /tmp
ls -al /tmp/

See logfiles in /var/log
ls -al /var/log

Read other users' bash history
cat /home/*/.bash_history

Find files with interesting extensions
find / -name "*.cfg" -or -name "*.config" -or -name "*.txt" -ls 2> /dev/null

Basic Example of usage:
We have been given a box to pen testing so we have taken the same process as most pen testing and done information gathering and run nmap scans.

• The only two ports that are open are 80 and 22
• We use Firefox to see if there any web page.
• We find there is a pretty simple web page that contains some information including email address.
• We then take these email address and produce a user list to use with hydra to brute force the ssh.
• After around 5 mins we get the username as john and passwords as password123.
• We then ssh into the box as the john using his password.
• We now want to try escalate our privileges so we can dump the shadow file and try to crack the other users password.
• We start with our basic privilege list above until we run find / \( -perm -2000 -or -perm -4000 \) -ls 2> /dev/null this tells us that the find command is running at suid
• We can use this to get a root shell by running find . -exec /bin/sh\; this will give us a euid of 0 meaning root.
• We can now use this to cat the /etc/shadow or ant other root task we want to complete on the box.

Please note this very basic example and depending on the system we may not want dump the hashes. I have just used this as its a very simple concept to explain.

Recommended Reading:
https://en.wikipedia.org/wiki/Setuid
https://en.wikipedia.org/wiki/User_identifier
http://g0tmi1k.blogspot.co.uk/2011/08/basic-linux-privilege-escalation.html

thank u jamie r like always good article i knew some of these technics but i have a question. I hack the ftp admin account then how can i esculate my priv? Its a linux server

Read the above article and the links it points to. Privilege escalation isn't an exact science. It depends a lot on what's on the server and what you have access to. The only way to get anywhere is to enumerate, test, fail, try again.

shadowzero excatly this why I tired to keep this simple with small example as if you never done any priv before its like where do you start.

sternone That is ture but most people with commom sense would make it so you can never login via ftp or ssh as root. You will login as a normal user then esculate your priv using sudo.

Great tutorial! Very easy to understand, and I just can't wait for the next one! 

for that service of-course but i want to get os level access any idea??

We don't know anything about the server you're accessing and you haven't given us any information about it other than you've got an ftp account.

Can you write files anywhere? Can you login as the same user using a different service? Are there other services running? Are there files you can download? Have you done enough enumeration and research?

Just because you've got access to one service, doesn't mean you can escalate it to a privileged user. It could be a dead end.

Shadowzero, i ran a brute force attack against admin account and i hacked it. So i can read, write, del files but i cant logon using that account to other services as i mentioned the server is Linux