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Security Baselines

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

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Security Baselines

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  1. Security Baselines Chapter 13

  2. 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 continued…

  3. 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

  4. 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)

  5. Network Operating System (NOS) • Includes special functions for connecting computers and devices into a LAN • Some have built-in networking functions

  6. 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

  7. OS/NOS Hardening

  8. Actions that Can DisruptFunctionality of a System • Attacks • Malfunctions • Errors

  9. 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 continued…

  10. 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

  11. 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

  12. Creating Needed User Groups • System administrator configures operating system to recognize certain user groups • Individual users are assigned to appropriate groups

  13. Configuring Access Controls • System administrator configures access controls for all protected files, directories, devices, and other objects

  14. 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 continued…

  15. 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

  16. 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

  17. 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

  18. Network Hardening • Crucial to have a network with availability as well as adequate security

  19. Firmware Updates • Made available by vendors as vulnerabilities and malfunctions are discovered with previous versions

  20. 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

  21. 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

  22. 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

  23. 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 continued…

  24. 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

  25. 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

  26. 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

  27. 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 continued…

  28. 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

  29. 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

  30. 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

  31. Cisco Discovery Protocol (CDP) TCP small servers UDPT small servers Finger HTTP server Bootp server Configuration autoloading IP source Proxy ARP Commonly Exploited Services on Cisco Platforms continued…

  32. 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

  33. 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

  34. Web servers E-mail servers FTP servers DNS servers NNTP servers File and print servers DHCP servers Data repositories Directory services Applications that Need Hardening

  35. Web Servers • Associated with more attacks and vulnerabilities than any type of server • Designed to make information accessible, rather than to protect it

  36. 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

  37. Isolating a Web Server on a DMZ

  38. 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

  39. 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

  40. FTP Servers • File Transfer Protocol • Used to transfer files between a workstation and an FTP server

  41. Vulnerabilities Associated with FTP • Protecting against bouncebacks • Restricting areas • Protecting usernames and passwords • Port stealing • Other documented vulnerabilities

  42. 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

  43. 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

  44. 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

  45. 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

  46. File and Print Servers • Store many of an organization’s most valuable and confidential information resources

  47. 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

  48. DHCP Servers • Dynamic Host Configuration Protocol (DHCP) • Software that assigns dynamic IP addresses to devices on a network • Reduces administrative burden • No security provisions

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