Unix Administration

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Unix Administration Guntis Barzdins Linux System Administration SYS ADMIN TASKS Setting the Run Level System Services User Management Network Settings Scheduling Jobs Quota Management Backup and Restore Adding and Removing software/packages Setting a Printer Monitoring the system (general, logs) Monitoring any specific services running. Eg. DNS, DHCP, Web, NIS, NPT, Proxy etc. Process Manipulation Once you run a program (e.g. vi, myprog,...), that program will suspend the terminal you called it in (the terminal will not be receiving input from you). You can start the program in the background to avoid this: myprog & You can suspend a program that is running and send it to background, if you already started it: Ctrl-z (to suspend) bg (sends the suspended program to the background) ps (show running processes) top (monitor running processes) kill (kill processes) & (send process to background) bg (send process to background) fg (get process from background) Ctrl+c (terminate process) Ctrl+z (suspend process) Intrusion Detection System (IDS) Open Source Tripwire – is a file integrity- checking program for UNIX/Linux operating systems Host-based Software that alerts you when important files change Tripwire keeps a hash value for each designated file When a file is altered/deleted, tripwire will have a new hash value that is different than the original Replaced by more advanced HIDS: OSSEC, Samhain, AIDE Client/Server mode etc. Tripwire tutorial in a slide Initial setup download / build / install it generate policy file # twadmin –create-polfile /etc/tripwire/twpol.txt modify policy file (e.g. remove unnecessary files) # vi /etc/tripwire/twpol.txt build initial database # tripwire –init check periodically # tripwire –check reconcile differences (e.g. software installation) # tripwire –update –accept-all –twrfile report_file Linux Security LINUX Firewall Linux Security SELinux Originally created by NSA to meet US DoD MAC Malicious or broken software can have root-level access to the entire system by running as a root process. SELinux (Security Enhanced Linux) provides enhanced security. Through SELinux policies, a process can be granted just the permissions it needs to be functional, thus reducing the risk SELINUX can take one of three values enforcing - SELinux security policy is enforced. permissive - SELinux prints warnings instead of enforcing. disabled - SELinux is fully disabled. Linux Security SELinux Configuration AppArmor Less complex and less secure Popular in user oriented distributions (Ubuntu, SUSE), enabled for some potentially vulnerable services by default Bundle software packages with AppArmor profiles Can create profile file by launching application in learning mode, can make secure enough profile if application not already compromised Capabilities: FS open/read/write different modes, networking (all/tcp/udp), executability etc. Log files On linux, you can go to /var/log Depends on the application Information shown in log files depend on the debug level you defined.

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Integrity Checking of Operating Systems with Respect to Kernel Level Malware”
To Bianca, for being who you are. Abstract Kernel-mode rootkits have gained a considerable momentum within the blackhat com- munity. They represent a considerable threat to any computer system, as they pro- vide an intruder with the ability to hide the presence of his malicious activity. These rootkits make changes to the operating system’s kernel, thereby providing particularly stealthy hiding techniques. Considering the kernel rootkit threat and other threats, the collection of reliable information from a compromised system becomes a central problem within the domain of computer security. This thesis addresses this problem. It looks at the possibility of using virtualization as a means to facilitate kernel-mode rootkit detection through integrity checking. The thesis describes several areas within the Linux kernel, which are commonly subverted by kernel-mode rootkits. It introduces the reader to the concept of virtual- ization and describes several technologies employing virtualization. The kernel-mode rootkit threat is then addressed through a description of their hiding methodologies. Some of the existing methods for malware detection are also addressed and analysed. A number of general requirements, which need to be satisﬁed by a general model enabling kernel-mode rootkit detection, are identiﬁed. A model addressing these requirements is suggested, and a framework implementing the model is set-up. The detection capabilities of the framework are tested on a couple of rootkits. iii Preface This report presents the results of my master thesis “Integrity checking of operating systems with respect to kernel level malware”. It is written as part of the Master de- gree (Sivilingeniør) in Computer Science at the Norwegian University of Science and Technology (NTNU), during Spring 2005.
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