Special Publication 800-41 Revision 1 (Draft) Guidelines on Firewalls and Firewall Policy (Draft) Recommendations of the National Institute of Standards and Technology Karen Scarfone Paul Hoffman NIST Special Publication 800-41 Guidelines on Firewalls and Firewall Revision 1 (Draft) Policy (Draft) Recommendations of the National Institute of Standards and Technology Karen Scarfone Paul Hoffman C O M P U T E R S E C U R I T Y Computer Security Division Information Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-8930 July 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Deputy Director GUIDELINES ON FIREWALLS AND FIREWALL POLICY (DRAFT) Reports on Computer Systems Technology The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the nation’s measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept implementations, and technical analysis to advance the development and productive use of information technology. ITL’s responsibilities include the development of technical, physical, administrative, and management standards and guidelines for the cost-effective security and privacy of sensitive unclassified information in Federal computer systems. This Special Publication 800-series reports on ITL’s research, guidance, and outreach efforts in computer security and its collaborative activities with industry, government, and academic organizations. National Institute of Standards and Technology Special Publication 800-41 Revision 1 (Draft) Natl. Inst. Stand. Technol. Spec. Publ. 800-41 rev1, 43 pages (Jul. 2008) Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessa rily the best available for the purpose. iii GUIDELINES ON FIREWALLS AND FIREWALL POLICY (DRAFT) Acknowledgements The authors, Karen Scarfone of the National Institute of Standards and Technology (NIST) and Paul Hoffman of the Virtual Private Network Consortium (VPNC), wish to thank their colleagues who reviewed drafts of this document and contributed to its technical content. The authors would like to acknowledge Tim Grance of NIST, and Matthew Goche, David Klug, Logan Lodge, John Pearce, Noel Richards, Anne Roudabush, and Steven Sharma of Booz Allen Hamilton, for their keen and insightful assistance throughout the development of the document. Special thanks go to Brahim Asfahani of Booz Allen Hamilton for his contributions to early drafts of the document. The authors also wish to express their thanks to the individuals and organizations that contributed to the original version of the publication, including John Wack of NIST and Ken Cutler and Jamie Pole of the MIS Training Institute, who authored the original version, and other contributors and reviewers— particularly Peter Batista and Wayne Bavry (U.S. Treasury); Harriet Feldman (Integrated Computer Engineering, Inc.); Rex Sanders (U.S. Geological Survey); and Timothy Grance, D. Richard Kuhn, Peter Mell, Gale Richter, and Murugiah Souppaya (NIST). Additional acknowledgements will be added to the final version of the publication. iv GUIDELINES ON FIREWALLS AND FIREWALL POLICY (DRAFT) Table of Contents Executive Summary..............................................................................................................ES-1 1. Introduction ......................................................................................................................1-1 1.1 Authority...................................................................................................................1-1 1.2 Purpose and Scope .................................................................................................1-1 1.3 Audience ..................................................................................................................1-1 1.4 Document Structure .................................................................................................1-1 2. Overview of Firewall Technologies ................................................................................2-1 2.1 Firewall Technologies ..............................................................................................2-2 2.1.1 Packet Filtering.............................................................................................2-2 2.1.2 Stateful Inspection ........................................................................................2-3 2.1.3 Application-Proxy Gateways.........................................................................2-5 2.1.4 Circuit-Level Gateways.................................................................................2-6 2.1.5 Dedicated Proxy Servers..............................................................................2-6 2.1.6 Virtual Private Networking ............................................................................2-8 2.2 Locations for Firewalls .............................................................................................2-8 2.2.1 Host-Based Firewalls and Personal Firewalls ..............................................2-9 2.2.2 Personal Firewall Appliances .....................................................................2-10 2.2.3 Distributed Firewalling ................................................................................2-10 2.3 Function-Specific Firewalls ....................................................................................2-10 2.3.1 PBX Firewall ...............................................................................................2-10 2.3.2 XML Firewall...............................................................................................2-11 2.3.3 Email Firewall .............................................................................................2-11 3. Firewalls and Network Architectures .............................................................................3-1 3.1 Network Layouts with Firewalls................................................................................3-1 3.2 Architecture with Multiple Layers of Firewalls ..........................................................3-3 4. Firewall Policy ..................................................................................................................4-1 4.1 Policies Based on IP Addresses and Protocols .......................................................4-1 4.1.1 IP Addresses and Other IP Characteristics ..................................................4-1 4.1.2 IPv6 ..............................................................................................................4-3 4.1.3 TCP and UDP...............................................................................................4-3 4.1.4 ICMP.............................................................................................................4-4 4.1.5 IPsec Protocols.............................................................................................4-4 4.2 Policies Based on Applications ................................................................................4-5 5. Firewall Planning and Implementation...........................................................................5-1 5.1 Plan..........................................................................................................................5-1 5.2 Configure .................................................................................................................5-3 5.2.1 Hardware and Software................................................................................5-3 5.2.2 Configure Rulesets .......................................................................................5-3 5.2.3 Configure Logging and Alerts .......................................................................5-4 5.3 Test ..........................................................................................................................5-4 5.4 Deploy......................................................................................................................5-5 5.5 Manage ....................................................................................................................5-5 5.6 General Recommendations .....................................................................................5-6 v GUIDELINES ON FIREWALLS AND FIREWALL POLICY (DRAFT) List of Appendices Appendix A— Glossary .......................................................................................................... A-1 Appendix B— Acronyms and Abbreviations ....................................................................... B-1 Appendix C— Resources ....................................................................................................... C-1 List of Figures Figure 2-1. TCP/IP Layers ........................................................................................................2-1 Figure 2-2. Packet Filter Used as Boundary Router .................................................................2-3 Figure 2-3. Typical Proxy Agents..............................................................................................2-5