Compromised System

Abstract

The following is a checklist of tasks to perform when a hosting system has been compromised, to ensure you have all the appropriate data to recover the system and ensure that it will not be compromised again. A key to rapid recovery is to use AED to minimize the forensic investigation time required to recover. Ideally the specific exploits should be identified in advance, however given time constraints this might not be possible until later. The goal of this checklist is Rapid Recovery.


Prerequisites

  • Backup server, to store 2 copies of data from the compromised system.
  • 1 valid AED subscription

Step 1) Find out how the system was compromised

First determine the level of compromise. Is this a full compromise, or just an individual site.

  • Start with your desktop and the desktop of anyone who accesses your system(s) as a privileged user. About 1/3 of all our forensic cases originate here. Of that 1/3, most of the time users believe that the desktop has not been compromised, and unfortunately most of the time it is!

    Please dont do that to yourself, time is of the essence, assume the desktop has been compromised. Its the easiest way to compromise a system, just steal the credentials on the desktop and log in!

  • general rootkit detection (note these tools are LIMITED. They are best used for initial inspections, they will miss a lot)

    • Using Rkhunter, run the following commands

      rkhunter --update
      rkhunter -c -sk
      

    • Using Chrootkit, run the following commands

      chkrootkit
      

  • Look for suspicious processes.

  • Look for suspicious files.

  • Create snapshots of memory

  • Boot system from trusted media (CD, PXE, etc)

  • Run “trusted” versions of chkrootkit and rkhunter against compromised drives

  • Investigate the following logfiles:

    /var/log/messages
    /var/log/secure
    

  • Confirm that your backups have not been compromised. Dont restore from a backup until you know you can trust it.

  • Image the compromised system if you can, but don’t trust anything it tells you.

Step 2) Back up data from the compromised host. We make 2 copies

  • Rsync back of compromised host from the backup server (it is because migration tools amost always miss something. This task will give you a complete copy of the old system)

    rsync -av -e ssh root@<IP>:/ /var/backups/<IP>/
    

  • On the compromised system, create a backup:

    mkdir /root/backups
    

    PSA 7.5 and Lower:

    /usr/loca/psa/bin/psadump -f | split -b1000m /root/backups/backup.
    

    PSA 8.0 and Higher:

    /usr/local/psa/bin/pleskbackup all --split=1G /root/backups/backup
    

  • Rsync back of compromised host from the backup server (this gets those backups too):

    rsync -av -e ssh root@<IP>:/ /var/backups/<IP>/
    

Step 3) Reinstall the system

  • Re-image the system

    wget -q -O - https://www.atomicorp.com/installer/aooi |sh
    

  • Update the system by running the following command

    yum -y update
    

  • Install/Configure Atomic Secured Linux run the following commands:

    wget -q -O - https://www.atomicorp.com/installers/asl |sh
    
    aum -u
    
    asl -s -f
    

  • Install Plesk by running the following command:

    wget -q -O - https://www.atomicorp.com/installer/atomic |sh
    

  • Install PSA and supported packages by running the following command:

    yum -y install psa psa-bu mailman psa-spamassassin frontpage
    

  • Copy psa.key from rsync backup on the backup server to /etc/psa/psa.key on the new system by running the following command:

    scp /backup/<IP>/etc/psa/psa.key  root@<IP>:/etc/psa/psa.key
    

  • Restart PSA by running the following command:

    /etc/init.d/psa restart
    

  • Log into PSA, and reconfigure settings. Specifically set the shared IP’s.

    https://<IP>:8443
    

Step 5) Restore system

  • Copy plesk backup to the re-imaged system:

    scp /var/backups/<IP>/root/backups/* root@<IP>:/root/
    

  • Use psastore/pleskstore to recover data:

    /usr/local/psa/bin/pleskrestore