[unisog] Developing "Security Guidelines" email

Joshua Beeman jbeeman at isc.upenn.edu
Fri Feb 25 20:15:21 GMT 2005


On occasion we have receive an email from an IT group on campus that says:

"Help!  We have a machine that we've wiped & built from scratch 3 times, 
and it keeps getting hacked.  What should we do?"

The problem from our perspective in issuing general guidelines to this type 
of request is that every school or center tends to be set up slightly 
different from the next.  That said however, we still hope to be able to 
provide a list of things to consider that will be helpful, stimulate new 
thought, etc.

Towards this end we came up with the list below.  Many of the items are 
biased towards the MS Windows OS.   If you maintain a similar list and/or 
have any feedback or comments, they would be greatly appreciated.

Thanks very much,

joshb

********************

1. P2P - If possible, remove any installed P2P software.  Emphasizing to 
the user that this is a common vector for spyware and unintended disclosure 
of information hopefully makes them think twice before reinstalling it 
right after you leave.

2. Strong Passwords / Common passwords - Make the user change their 
password and enforce strong passwords.  If the user is using the same 
username/password combination they were the first time the machine was 
compromised, or if the user has a weak password, it may not matter whether 
the box was effectively rebuilt or patched.  Additionally, consider if you 
are using the same username/password combination (e.g. - local 
administrator password, generic accounts) on multiple machines.  A 
compromise on one machine may effect the integrity of multiple machines in 
your domain or on your network.  Another reason to enforce strong 
passwords, or longer passphrases, and change them periodically.

3. Software firewall - Enable the integrated firewall or install a software 
firewall to block incoming connections.  If it is a server, or simply a 
critical host, consider a hardware firewall of the appropriate scale.

4. Anti-Virus - Make sure that the latest version of the anti-virus client 
is installed and that the definitions are up to date.  If you are not 
already, consider running a managed solution that allows you to push AV 
definitions and upgrades from a central location 
(http://www.upenn.edu/computing/virus/manage-sw.html).

5. OS Patches/SUS service - Make sure that the operating system is up to 
date at all times.  If you are not already, consider running a SUS or SMS 
server, or participating in the University's SUS program 
(http://www.upenn.edu/computing/sus/).   Additionally, for Windows 
machines, consider using the Microsoft Baseline Security Analyzer to 
identify vulnerabilities in the OS as well as certain applications 
(http://www.microsoft.com/technet/security/tools/mbsahome.mspx).

6. IPSEC filtering - Consider deploying Microsoft's IPSEC as a Group Policy 
on your domain, or at the very least, on individual hosts.  IPSEC has two 
functions:
         a) to protect the contents of IP packets (data integrity) and
         b) to provide a defense against network attacks through packet 
filtering and the enforcement of trusted communication (availability)

With IPSEC filtering in place, you can restrict incoming & outgoing traffic 
with a granularity not typically associated with integrated software 
firewalls.  You can significantly limit, in real-time, the potential for 
internal & external (Penn & non-Penn source) exploits with custom rule-sets 
that are specific to your environment, to a particular host, or even to a 
particular exploit that happens to be circulating.

A quick search of the Microsoft website will turn up a number of documents 
relating to this topic.  I this is one of the clearer MS IPSEC overviews 
(sorry for the long URL):
http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/windowsxp/home/using/productdoc/en/sag_IPSECconcept.asp

7. Create & Apply security templates -  Using the Microsoft Management 
Console with the "Security Configuration and Analysis" and the "Security 
Templates" snap-ins, you can load default policy templates with varying 
degrees of strictness, such as "SECUREWS" (secure workstation) and 
"HISECUREWS" (highly secure workstation), and then compare your current 
configuration to these templates.  After reviewing the differences, you can 
save your own template based on the default recommendations and your 
organizations needs and apply this template to computers that you support 
individually or through a Group Policy.  Here is some sample documentation 
from MS:
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/sag_scedefaultpols.mspx

9. Imaging - If you are using disk imaging (e.g. - Ghost) to repair 
infected machines and you see compromises quickly *after* re-imaging a 
host, you may need to consider checking the base image for vulnerabilities 
such as the ones listed above and possibly rebuild it.   If you are unsure 
about the image and want to set up a test host for Security to do a 
full-blown vulnerability scan, just contact our office at 
security at isc.upenn.edu.   Make sure if you request this that it is a test 
or unused system, as a full-scan of this nature can be destructive.

10. Restrict end-user privileges - If you are not already doing it, you may 
wish to restrict standard end-users with policies and profiles from having 
the ability to install applications or modify the PC configuration in any 
way.  Obviously, this may not work for all environments.



--
Joshua Beeman
Sr. Information Security Specialist
University of Pennsylvania
jbeeman at isc.upenn.edu
(215) 573-6798
http://www.upenn.edu/computing/security

What is the single most valuable piece of data on your computer?  Is it 
backed up? 





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