security baselines chapter 13. learning objectives gain an understanding of os/nos vulnerabilities...
TRANSCRIPT
Security Baselines
Chapter 13
Learning Objectives
Gain an understanding of OS/NOS vulnerabilities and hardening practices
Understand the operation of a file system and how to secure a file system
Explore common network hardening practices, including firmware updates and configuration best practices
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Learning Objectives
Identify network services commonly exploited by attackers and learn best practices for writing access control lists
Explore vulnerabilities regarding network services such as Web, FTP, DNS, DHCP, Mail, File/Print Servers and Data Repositories as well as best practices in securing such services
Operating System (OS)
Performs basic tasks Recognizes input from keyboard Sends output to display screen Keeps track of files and directories on the disk Controls peripheral devices (disk drives,
printers)
Network Operating System (NOS)
Includes special functions for connecting computers and devices into a LAN
Some have built-in networking functions
OS/NOS Hardening
Process of modifying an OS’s default configuration to make it more secure to outside threats
May include removal of unnecessary programs and services
May include application of patches to system kernel to limit vulnerability
OS/NOS Hardening
Actions that Can DisruptFunctionality of a System
Attacks Malfunctions Errors
Best Practices for System Hardening
Remove unused applications, services, and unused or unnecessary file shares
Implement and enforce strong password policies; remove or disable expired or unneeded accounts
Limit number of administrative accounts Set account lockout policies to discourage
password cracking
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Best Practices for System Hardening
Keep track of latest security updates and hot fixes
Maintain logging of all user account and administrative activity
Back up the system periodically Keep external log of each critical system Maintain records of backups and upgrades
File Systems
Store data that enable communication between an application and its supporting disk drives
Setting privileges and access controls protect information stored on the computer
Common privileges: read, write (modify), lock, append, and execute
Group users by common needs Additional rights can be granted to a single user in a
group Principle of least privilege
Creating Needed User Groups
System administrator configures operating system to recognize certain user groups
Individual users are assigned to appropriate groups
Configuring Access Controls
System administrator configures access controls for all protected files, directories, devices, and other objects
Common Practices for Setting File and Data Privileges
Disable write and execute privileges for all executable and binary files
Restrict access of OS source files, configuration files, and their directories
For UNIX systems: No world-writable files unless specifically
required Mount files systems as read only and nosuid
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Common Practices for Setting File and Data Privileges
For NT systems No permissions allowing “Everyone” group to modify
files Assign access permission of immutable to all
kernel files Establish all log files as “append only” Prevent users from installing, removing, or
editing scripts Pay attention to access control inheritance when
defining categories of files and users
Installing and Configuring File Encryption Capabilities
File encryption is useful if the OS Lacks adequate access controls to maintain
confidentiality Does not support access control lists
Encryption is resource-consuming; carefully weigh benefits
Systematic Approach forAddressing Updates
Establish procedures for monitoring security-related information
Evaluate updates for applicability Plan installation of applicable updates Install updates using a documented plan Deploy new systems with latest software
Network Hardening
Crucial to have a network with availability as well as adequate security
Firmware Updates
Made available by vendors as vulnerabilities and malfunctions are discovered with previous versions
Configuration
Routing functions Designed to route packets efficiently and
reliably, but not securely Not to be used to implement a security policy
Firewall systems Should govern security of information flow in
and out of the network Provide a policy enforcement mechanism at a
security domain boundary
Assigning Network Addresses for Interfaces on a Firewall Device
For the Internet Obtain IP addresses from ISP that connects to
the firewall For internal networks
Obtain IP addresses from within the organization, typically from RFC 1918 specification
Establishing Routing Configuration
Should be performed in an environment isolated from the production network
Should specify what connectivity is to be permitted with the specific statements and deny all other connectivity
Derived from network topology; should not be used to implement aspects of a security policy
Best Practices for Configuring Router and Firewall Systems
Keep copy of current configurations of network devices in safe location
Never allow IP-directed broadcasts through the system
Configure devices with meaningful names Use a description for each interface Specify bandwidth on the interfaces
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Best Practices for Configuring Router and Firewall Systems
Configure a loopback address Handle SNMP with care Avoid common names for password and
naming schemes Deploy logging about interface status,
events, and debugging Restrict data traffic to required ports and
protocols only
Access Control List (ACL)
Set of data that informs a computer’s OS which permissions (access rights) each user or group has to a specific system object
Control flow of packets through a device based on certain parameters and information contained within a packet
Implement a certain type of security policy, but not considered a policy by themselves
Implement packet filtering
Packet Filtering
Process of deciding disposition of each packet that can pass through a router
Provides basic protection mechanism for a routing firewall device through inspection of packet contents
Can be based on intrinsic or extrinsic information pertaining to a data packet
Best Practices for Designing Filtering Rules for New Networks
Add “deny all” rule to articulate the security policy more completely
Design antispoofing rules and place them at top of the ACL
Identify protocols, ports, and source and destination addresses that need to be serviced
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Best Practices for Designing Filtering Rules for New Networks
Configure filtering rule set of the ACL by protocol and by port
Collapse matching protocols rows and consecutive ports rows together into one new row that specifies a range
Place all permission rules between antispoofing rules and “deny all” rule at the end of the rule set
Enabling and Disabling of Services and Protocols
Many services can be easily targeted by attackers unless disabled by system administrators
Evaluate every service for need and risks; remove unnecessary ones
Evaluate and install required services in a manner to lower potential risk
Commonly Exploited Services
Remote Procedure Call (RPC) Network File System (NFS) Web services Simple Mail Transfer Protocol (SMTP) Bootstrap Protocol DoS attacks are successful when
unnecessary services are running on network devices
Commonly Exploited Services on Cisco Platforms
Cisco Discovery Protocol (CDP) TCP small servers UDPT small servers Finger HTTP server Bootp server Configuration autoloading IP source Proxy ARP
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Commonly Exploited Services on Cisco Platforms
IP-directed broadcast Classless routing behavior IP unreachable notifications IP mask relay IP redirects NTP service Simple Network Management Protocol Domain Name Service
Application Hardening
Process of making applications software secure by ensuring that the software contains security enabling technology: Sign in capabilities for authenticated network
connections Ability to run properly in secured
configurations
Applications that Need Hardening
Web servers E-mail servers FTP servers DNS servers NNTP servers
File and print servers
DHCP servers Data repositories Directory services
Web Servers
Associated with more attacks and vulnerabilities than any type of server
Designed to make information accessible, rather than to protect it
High Level Best Practices for Securing Web Servers
Isolate a Web server on a DMZ Configure a Web server for access
privileges Identify and enable Web server-specific
logging tools Consider security implications Configure authentication and encryption
Isolating a Web Server on a DMZ
E-mail Servers
Serious risks associated with ability to receive e-mail from the outside world Attachments with malicious contents E-mails with abnormal MIME headers Scripts embedded into HTML-enabled mail
Protecting Against E-mail Vulnerabilities
Use latest software updates and patches on e-mail server
Deploy dedicated e-mail relay (gateway) server between internal network and Internet
Deploy virus-scanning tools on the server Use attachment-checking mechanisms on the
server Use HTML Active Content removal
FTP Servers
File Transfer Protocol Used to transfer files between a workstation
and an FTP server
Vulnerabilities Associated with FTP
Protecting against bouncebacks Restricting areas Protecting usernames and passwords Port stealing Other documented vulnerabilities
DNS Servers
Domain Name Service (DNS) Collective name for system of servers that
translate names into addresses in a process transparent to the end user
Vulnerabilities Associated with DNS
Inaccurate data on IP address ownership Customer registry communication DNS spoofing and cache poisoning Out-of-date root.hints file Recursive queries Denial-of-service attacks
NNTP Servers
Network News Transfer Protocol (NNTP) Delivers news articles to users on the Internet Stores articles in a central database; users choose only
items of interest Makes few demands on structure, content, or storage
of news articles NNTP servers can index and cross reference
messages, and allow for notification of expiration
NNTP Servers
Similar vulnerabilities to other network services
Effective methods of preventing attacks Use proper authentication mechanisms Disable unneeded services Apply relevant software and OS patches
File and Print Servers
Store many of an organization’s most valuable and confidential information resources
Protecting Against File and Print Server Vulnerabilities
Offer only essential network and OS services on a server
Configure servers for user authentication Configure server operating systems Manage logging and other data collection
mechanisms Configure servers for file backups
DHCP Servers
Dynamic Host Configuration Protocol (DHCP) Software that assigns dynamic IP addresses to
devices on a network Reduces administrative burden No security provisions
Preventing Attacks on DHCP Servers
Assign permanent addresses Collect Media Access Control (MAC)
addresses of all computers on network and bind them to corresponding IP addresses
Use dynamic addressing, but monitor log files
Use intrusion detection tools
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Preventing Attacks on DHCP Servers
Configure DHCP server to force stations with new MAC addresses on the network to register with the DHCP server
Implement latest software and patches
Data Repositories
Store data for archiving and user access Contain an organization’s most valuable
assets in terms of information Should be carefully protected
Directory Services
Lightweight Directory Access Protocol (LDAP) Industry standard protocol for providing
networking directory services for the TCP/IP model
Can store and locate information about entities and other network resources
Based on simple, treelike hierarchy called a Directory Information Tree (DIT)
Directory Service-Oriented Threats
Unauthorized access to data by monitoring or spoofing authorized users’ operations
Unauthorized access to resources by physically taking over authenticated connections and sessions
Unauthorized modification or deletion of data or configuration parameters
Spoofing of directory services Excessive use of resources
Nondirectory Service-Oriented Threats
Common network-based attacks against LDAP servers to compromise availability of resources
Attacks against hosts by physically accessing the resources
Attacks against back-end databases that provide directory services
Security of LDAP Is Dependent on…
Authentication Anonymous Simple Simple Authentication and Security Layer
(SASL) for LDAPv3 Authorization
Principles of Securityto Protect Databases
Authentication of users and applications Administration policies and procedures Initial configuration Auditing Backup and recovery procedures
Chapter Summary
Role of operating and file systems as they relate to security of information resources stored on computer systems
Operating system vulnerabilities Use of OS hardening practices to prevent
attacks and system failures
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Chapter Summary
Vulnerabilities associated with common services installed on computer systems (WWW services, FTP, DNS) and best practices in protecting against threats to these services
Maintenance and upgrade of computer systems