host hardening (march 21, 2011) © abdou illia – spring 2011
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Host Hardening
(March 21, 2011)
© Abdou Illia – Spring 2011
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CERT Report on systems vulnerabilities
Source: CERT Report @ http://www.kb.cert.org/vuls/bymetric
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OS market share for 2006
OS Vulnerability test Source: http://www.omninerd.com/articles/2006_Operating_System_Vulnerability_Summary
OS tested: Win XP, Win Server 2003, Win Vista Ultimate, Mac OS Classic, OS X 10.4 Server, OS X 10.4 Tiger FreeBSD 6.2, Solaris 10, Fedora Core 6, Slackware 11.0, Suse Enterprise 10,
Ubuntu 6.10 Tools used to test vulnerabilities:
Scanning tools (Track, Nessus) Network mapping (Nmap command) All host with OS installation defaults
Results Microsoft's Windows and Apple's OS X are ripe with remotely accessible
vulnerabilities and allow for executing malicious code The UNIX and Linux variants present a much more robust exterior to the outside Once patched, however, both Windows and Apple’s OS are secure, at least
from the outside.
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Your knowledge about Host hardening
Today, how long it will take for a hacker to “own” a server with OS installation defaults that is connected to the Internet?
a) A week
b) A day or two
c) Two weeks
What needs to be done, first, in order to prevent a hacker from taking over a server with OS installation defaults that has to be connected to the Internet?
a) Lock the server room
b) Configure the firewall to deny all inbound traffic to the server
c) Download and install patches for known vulnerabilities
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Your knowledge about Host hardening
You performed an Out-of-the-box installation of Windows XP and Linux FreeBSD 6.2 on two different computers. Which computer is more likely to be secure ?
a) Windows XP
b) Linux FreeBSD 6.2
c) They will have the same level of security
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What is Hardening Host Computers?
A series of actions to be taken in order to make it hard for an attacker to successfully attack computers in a network environment
Because it’s easy to overlook something in the hardening process, businesses need to adopt a standard hardening methodology or a standard security baseline
Need to have different security baseline for different kind of host; i.e.
Different security baselines for different OS and versions Different security baselines for different types of servers
(web servers, mail servers, etc.) and applications
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Security Baseline
Organization could use different standards OS vendors’ baselines and tools
e.g. Follow MS Installation procedure and use Microsoft Baseline Security Analyzer (MBSA)
Standards Agencies baselines e.g. CobiT* Security Baseline
Company’s own security baselines Security Baseline to be implemented by
Server administrators known as systems admin
* Control Objectives for Information and Related Technology
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Elements of Hardening
Physical security Secure installation and configuration Fix known vulnerabilities Remove/Turn off unnecessary services (applications) Harden all remaining applications Manage users and groups Manage access permissions
For individual files and directories, assign access permissions to specific users and groups
Back up the server regularly Advanced protections
According to
baseline
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Example of Security Baseline for Win XP Clients OS Installation
Create a single partition on HDD Format disk using NTFS file system Install Win XP and Service Pack 3
Fixing OS vulnerabilities Download and install latest patches Turn on Windows’ Automatic Updates checking
Configure Windows Firewall Block incoming connections except KeyAccess and Remote
Assistance Turn off unnecessary services
Turn off Alerter, Network Dynamic Data Exchange, telnet Application Installation
Centrally assign applications using group policies Fixing applications’ vulnerabilities
Turn on each application’s automatic update checking
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Hardening servers Be aware of the 5 ‘P’ s of security and compliance
Proper Planning Prevents Poor Performance Plan the installation
Identify The purpose of the server. Example: provides easy & fast access to Internet
services The services provided on the server Network service software (client and server) The users or types of users of the server
Determine Privileges for each category of users If and how users will authenticate How appropriate access rights will be enforced Which OS and server applications meet the requirements The security baseline(s) for installation & deployment
Install, configure, and secure the OS according to the security baseline Install, configure, and secure server software according to sec. baseline Test the security Add network defenses Monitor and Maintain
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Hardening servers (cont.)
Choose the OS that provides the following: Ability to restrict admin access (Administrator vs. Administrators) Granular control of data access Ability to disable services Ability to control executables Ability to log activities Host-based firewall Support for strong authentication and encryption
Disable or remove unnecessary services or applications Remove rather than disable to prevent re-enabling Additional services increases the attack vector More services can increase host load and decrease performance Reducing services reduces logs and makes detection of intrusion easier
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Hardening servers (cont.)
Configure user authentication Remove or disable unnecessary accounts
(e.g. Guest account) Change names and passwords for default accounts Disable inactive accounts Assign rights to groups not individual users Don't permit shared accounts if possible Configure time sync Enforce appropriate password policy Use 2-factor authentication when necessary Always use encrypted authentication
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Windows Hardening Most Windows hardening done using Graphical
User Interface
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Windows Hardening Turning services and applications on/off in Windows
Q: Reducing services can increase host load and decrease performance: T F
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Windows Hardening
Domain configuration and directory service needed for central security setting
Windows 2000 introduced hierarchical domain structure with Active Directory
Domain is a collection of resources
Domain contains one or more domain controllers, member servers, client PCs
Group policy objects (GPOs) on a domain controller can implement security policies throughout a domain
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UNIX / Linux Hardening
Many versions of UNIX No standards guideline for hardening
User can select the user interface Graphic User Interface (GUI) Command-Line Interfaces (CLIs) or shells
CLIs are case-sensitive with commands in lowercase except for file names
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UNIX / Linux Hardening
Three ways to start services
inetd program used to start services when requests come in from users
rc scripts to start services automatically at boot up
Start a service manually by typing its name or executing a batch file that does so
Inetd = Internet daemon; i.e. a computer program that runs in the background
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UNIX / Linux Hardening
Program A
Program B
Program C
Program D
inetd
Port 23 Program APort 80 Program BPort 123 Program CPort 1510 Program D
1. Client RequestTo Port 123
4. Start and Process
This Request
3. Program C 2. Port 123
/etc/inetd.config
Starting services upon client requests Services not frequently used are dormant Requests do not go directly to the service Requests are sent to the inetd program which is started at server boot up
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UNIX / Linux Hardening
Turning On/Off unnecessary Services In UNIX
Identifying services running at any moment
ps command (processor status), usually with –aux parameters, lists running programs
Shows process name and process ID (PID)
netstat tells what services are running on what ports
Turning Off Services In UNIX kill PID command is used to kill a particular process
kill 47 (If PID=47)
Q: You kill some services but see that they are running again the next day. Explain why?
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Advanced Server Hardening Techniques
Need to read Event Logs to diagnose problems
Failed logins, changing permissions, starting programs, kernel messages, etc.
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Advanced Server Hardening Techniques
File Encryption Protects files even if attacker breaks in Key escrow: Copy of encryption key is kept
elsewhere to protect in case of key loss Windows Encrypting File System (EFS)
Select file in Windows Explorer, select Properties Click on General tab’s Advanced button Click on the box Encrypt contents to secure data
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Advanced Server Hardening Techniques
File Integrity Checker
Creates snapshot of files: a hashed signature (message digest) for each file
After an attack, compares post-hack signature with snapshot
This allows systems administrator to determine which files were changed
Tripwire is a file integrity checker for Linux/UNIX, Windows, etc.: www.tripwire.com (ftp://coast.cs.purdue.edu/pub/tools/unix)
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Advanced Server Hardening Techniques
File 1File 2…Other Files inPolicy List
File 1File 2…Other Files inPolicy List
File 1 SignatureFile 2 Signature……
File 1 SignatureFile 2 Signature……
Tripwire
Tripwire
1.EarlierTime
2.After
Attack
Post-Attack Signatures
3. Comparison to Find Changed Files
Reference Base
File Integrity problem: many files change for legitimate reasons. So it is difficult to know which ones the attacker changed.
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Other types of host that can be Hardened Internetwork Operating System (IOS)
For Cisco Routers, Some Switches, Firewalls Even cable modems with web-based
management interfaces
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