Download Security+ Guide to Network Security Fundamentals

Security Baselines
Learning Objectives
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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
continued…
Learning Objectives
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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)
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Performs basic tasks
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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)
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Includes special functions for connecting
computers and devices into a LAN
Some have built-in networking functions
OS/NOS Hardening
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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 Disrupt
Functionality of a System
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Attacks
Malfunctions
Errors
Best Practices for System Hardening
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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
continued…
Best Practices for System Hardening
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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
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Store data that enable communication between an
application and its supporting disk drives
Setting privileges and access controls protect
information stored on the computer
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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
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System administrator configures operating
system to recognize certain user groups
Individual users are assigned to appropriate
groups
Configuring Access Controls
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System administrator configures access
controls for all protected files, directories,
devices, and other objects
Common Practices for Setting File and
Data Privileges
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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:
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No world-writable files unless specifically
required
Mount files systems as read only and nosuid
continued…
Common Practices for Setting File and
Data Privileges
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For NT systems
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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
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File encryption is useful if the OS
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Lacks adequate access controls to maintain
confidentiality
Does not support access control lists
Encryption is resource-consuming;
carefully weigh benefits
Systematic Approach for
Addressing Updates
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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
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Crucial to have a network with availability
as well as adequate security
Firmware Updates
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Made available by vendors as
vulnerabilities and malfunctions are
discovered with previous versions
Configuration
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Routing functions
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Designed to route packets efficiently and
reliably, but not securely
Not to be used to implement a security policy
Firewall systems
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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
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For the Internet
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Obtain IP addresses from ISP that connects to
the firewall
For internal networks
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Obtain IP addresses from within the
organization, typically from RFC 1918
specification
Establishing Routing Configuration
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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
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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
continued…
Best Practices for Configuring Router
and Firewall Systems
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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)
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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
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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
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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
continued…
Best Practices for Designing Filtering
Rules for New Networks
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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
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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
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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
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Cisco Discovery Protocol (CDP)
TCP small servers
UDPT small servers
Finger
HTTP server
Bootp server
Configuration autoloading
IP source
Proxy ARP
continued…
Commonly Exploited Services on Cisco
Platforms
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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
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Process of making applications software
secure by ensuring that the software
contains security enabling technology:
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Sign in capabilities for authenticated network
connections
Ability to run properly in secured
configurations
Applications that Need Hardening
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Web servers
E-mail servers
FTP servers
DNS servers
NNTP servers
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File and print
servers
DHCP servers
Data repositories
Directory services
Web Servers
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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
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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
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Serious risks associated with ability to
receive e-mail from the outside world
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Attachments with malicious contents
E-mails with abnormal MIME headers
Scripts embedded into HTML-enabled mail
Protecting Against E-mail Vulnerabilities
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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
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File Transfer Protocol
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Used to transfer files between a workstation
and an FTP server
Vulnerabilities Associated with FTP
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Protecting against bouncebacks
Restricting areas
Protecting usernames and passwords
Port stealing
Other documented vulnerabilities
DNS Servers
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Domain Name Service (DNS)
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Collective name for system of servers that
translate names into addresses in a process
transparent to the end user
Vulnerabilities Associated with DNS
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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
DNS Server Attack
Remote file copy
NNTP Servers
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Network News Transfer Protocol (NNTP)
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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
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Similar vulnerabilities to other network
services
Effective methods of preventing attacks
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Use proper authentication mechanisms
Disable unneeded services
Apply relevant software and OS patches
File and Print Servers
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Store many of an organization’s most
valuable and confidential information
resources
Protecting Against File and Print Server
Vulnerabilities
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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
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Dynamic Host Configuration Protocol
(DHCP)
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Software that assigns dynamic IP addresses to
devices on a network
Reduces administrative burden
No security provisions
Preventing Attacks on DHCP Servers
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Assign permanent addresses
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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
continued…
Preventing Attacks on DHCP Servers
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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
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Store data for archiving and user access
Contain an organization’s most valuable
assets in terms of information
Should be carefully protected
Directory Services
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Lightweight Directory Access Protocol
(LDAP)
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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 Services
Directory Service-Oriented Threats
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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
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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…
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Authentication
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Anonymous
Simple
Simple Authentication and Security Layer
(SASL) for LDAPv3
Authorization
Principles of Security
to Protect Databases
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Authentication of users and applications
Administration policies and procedures
Initial configuration
Auditing
Backup and recovery procedures
Summary
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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
continued…
Summary (Cont.)
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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