Thursday, December 12, 2013

Live Forensic on Linux

Last month, I wrote a bit about doing live forensic on a Windows machine. Today, let's do Linux.

Let's do a bit of recall before we proceed. Since I'm lazy to repeat, here are excerpts of what I have written previously in Live Forensic on Windows:

Before we touch that, why do we need to do live forensic at the first place? For a few reasons:
a) It is a production server and the Business Owner or System Admin would not let you shut down the system/server for offline forensic
b) The server/system is at a location that you could not go there physically
c) We afraid that we may lost crucial information e.g. malware that runs in memory only if we were to shut down the system immediately

Next, what info or data should we gather? What tools to use? In IT Forensic, we normally talk about using trusted binaries. Why is it important? Because on a hacked or malware infected machines, it is not uncommon for the attacker/malware to install rootkits or replace some common commands/binaries of the system/server in order to hide or cover their tracks. Running these binaries might not give you the real output or info as they should be. Therefore, the first steps is to prepare a forensic kit (e.g. write protected USB stick, CD) with your trusted binaries/tools.

Now, what tools you can use? Unlike Windows, Linux binaries are quite sensitive to the kernel's version. Also, have you heard about dynamic library dependency hell? Basically one library depends on other library which depends on another libraries and so on... Thus, most of the time you can't just copy out the binary/program and expect it to work on another system. You can always compile your own binary statically, but that require lots of works as well. Luckily, I found a saviour - Busybox! Yes, it is the same tool you use to run commands on your rooted Android devices :)

So, go grab yourself the Linux version of Busybox now!

For memory dump acquisition:
1. Use LiME. However, it might not work if the system prevent loading of kernel module. it is also very kernel specific, thus you can't compile it on a system and expect it to work on any systems. It will only work on a system with a same kernel version. 
2.  dd if=/dev/mem of=host1/dd-dev-mem.img . However, this may not work with newer kernel or if the kernel is compiled with STRICT_DEVMEM=y option (check /boot/config-<KERNELVERSION>). 

Have fun!

What to Acquire
Tools/Commands to Use (Output is saved to a file)
·         ./busybox-i686 hostname > targethost/b-hostname.txt
·         hostname > targethost/hostname.txt
OS version
·         ./busybox-i686 uname –a > targethost/b-uname-a.txt
·         uname –a > targethost/uname-a.txt
·         cat /etc/os-release > targethost/os-release.txt
Current system date and time
·         ./busybox-i686 date > targethost/b-date.txt
·         date > targethost/date.txt
Current IP address
·         ./busybox-i686 ifconfig > targethost/b-ifconfig.txt
·         ifconfig –a > targethost/ifconfig-a.txt
Current running process list
·         ./busybox-i686 ps –eaf > targethost/b-ps-eaf.txt
·         ps –eaf > targethost/ps-eaf.txt
·         ./busybox-i686 lsof  –a > targethost/b-lsof.txt
·         lsof > targethost/lsof.txt  
 current network connection lis
·         ./busybox-i686 netstat –anp > targethost/b-netstat-anp.txt
·         netstat –anp > targethost/netstat-anp.txt
·         ./busybox-i686 netstat –anr > targethost/b-netstat-anr.txt
·         netstat –anr > targethost/netstat-anr.txt
 current list of current logon sessions
·         ./busybox-i686 who –a > targethost/b-who-a.txt
·         who –a > targethost/who-a.txt
·         w > targethost/w.txt
 list of auto start applications and services
·         chkconfig --list > targethost/chkconfig--list.txt
·         ./busybox-i686 ls –alR /etc/rc* > targethost/ls-al-etc-rc.txt
·         ./busybox-i686 ls –alR /etc/init.d > targethost/ls-al-rc-d.txt
·         more /etc/init.d/* > targethost/more-init-d.txt
·         cat /etc/inittab > targethost/inittab.txt
·         service –-status-all > targethost/service—status-all.txt
·         ./busybox-i686 ls -alR /etc/systemd* > targethost/ls-al-etc-systemd.txt
·         ./busybox-i686 cat /etc/inetd.conf > targethost/inetd.conf
·         cat /etc/inetd.conf > targethost/inetd.conf
 environment variables
·         ./busybox-i686 env > targethost/b-env.txt
·         env > targethost/env.txt
 list of cron jobs (scheduler)
·         ./busybox-i686 cat /etc/crontab > targethost/b-crontab.txt
·         cat /etc/crontab > targethost/crontab.txt
 system event (dmesg) log records
·         ./busybox-i686 dmesg > targethost/b-dmesg.txt
·         dmesg > targethost/dmesg.txt
 last user activity records
·         ./busybox-i686 last > targethost/b-last.txt
·         last > targethost/last.txt
·         lastb > targethost/lastb.txt
·         lastlog > targethost/lastlog.txt
 list of installed software
·         rpm –qa targethost/rpm-qa.txt
·         dpkg --get-selections > targethost/dpkg—get-selections.txt
 list of user accounts
·         ./busybox-i686 cat /etc/passwd > targethost/b-passwd.txt
·         cat /etc/passwd > targethost/passwd.txt
·         ./busybox-i686 cat /etc/group > targethost/b-group.txt
·         cat /etc/group > targethost/group.txt
 partition table and drive info
·         ./busybox-i686 df –h > targethost/b-df-h.txt
·         df –h > targethost/df-h.txt
·         ./busybox-i686 fdisk -l > targethost/b-fdisk-l.txt
·         fdisk -l > targethost/fdisk-l.txt
·         parted –l targethost/parted-l.txt
·         ./busybox-i686 cat /etc/fstab > targethost/b-fstab.txt
·         cat /etc/fstab > targethost/fstab.txt
·         ./busybox-i686 mount > targethost/b-mount.txt
·         mount > targethost/mount.txt
 list of loaded modules
·         ./busybox-i686 lsmod > targethost/b-lsmod.txt
·         lsmod > targethost/lsmod.txt
·         ./busybox-i686 cat /proc/modules > targethost/b-proc-modues.txt
·         cat /proc/modules > targethost/proc-modues.txt
 information about memory usage
·         ./busybox-i686 cat /proc/meminfo > targethost/b-proc-meminfo.txt
·         cat /proc/meminfo > targethost/proc-meminfo.txt

 iptables rules (firewall)
·         iptables --list > targethost/iptables--list.txt
 system logs normally stored in /var/log
·         ./busybox-i686 tar –czvf targethost/b-var-log.tgz /var/log
 memory dump with LiME
As the LiME software needs to be specially built for the target system Linux’s kernel, there are more steps to be done before the tool can be used:
a.     Extract the LiME source file you downloaded.
b.     Change directory into the “src” directory. Type: cd src
c.     Compile the module. Type: make
·         If successful, a new file starting with “lime’ and ending with “.ko” will be created. Example: lime-3.2.6.ko
·         insmod lime*.ko “path=targethost/lime.mem format=lime”
The module is then loaded to the kernel and the memory dump will happen automatically. If you need to run it again, you must first remove the module from the kernel. Type: rmmod lime

 /dev/mem and /dev/kmem via dd
·         dd if=/dev/mem of=targethost/dd-dev-mem.img
·         dd if=/dev/kmem of=targethost/dd-dev-kmem.img

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