1、BSI Standards Publication BS ISO/IEC 27033-5:2013 Information technology Security techniques Network security Part 5: Securing communications across networks using Virtual Private Networks (VPNs)BS ISO/IEC 27033-5:2013 BRITISH STANDARD National foreword This British Standard is the UK implementation
2、 of ISO/IEC 27033-5:2013. It supersedes BS ISO/IEC 18028-5:2006 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee IST/33, IT - Security techniques. A list of organizations represented on this committee can be obtained on request to its secretary. This p
3、ublication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013 ISBN 978 0 580 65102 1 ICS 35.040 Compliance with a British Standard cannot confer imm
4、unity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2013. Amendments issued since publication Date Text affectedBS ISO/IEC 27033-5:2013 Information technology Security techniques Network security Part 5: Se
5、curing communications across networks using Virtual Private Networks (VPNs) Technologies de linformation Techniques de scurit - Scurit de rseau Partie 5: Scurit des communications au travers des rseaux utilisant des rseaux privs virtuels (VPNs) ISO/IEC 2013 INTERNATIONAL STANDARD ISO/IEC 27033-5 Fir
6、st edition 2013-08-01 Reference number ISO/IEC 27033-5:2013(E)BS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E)ii ISO/IEC 2013 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwi
7、se in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ca
8、se postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) ISO/IEC 2013 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references 1 3 T erms and
9、 definitions . 1 4 Abbreviations. 2 5 Document structure 2 6 Overview . 2 6.1 Introduction 2 6.2 Types of VPNs 3 7 Security Threats 4 8 Security Requirements 5 8.1 Overview 5 8.2 Confidentiality . 5 8.3 Integrity 6 8.4 Authenticity . 6 8.5 Authorization . 6 8.6 Availability 6 8.7 Tunnel Endpoint Sec
10、urity 6 9 Security Controls 6 9.1 Security aspects . . 6 9.2 Virtual circuits . 7 10 Design Techniques 7 10.1 Overview 7 10.2 Regulatory and legislative aspects . 8 10.3 VPN management aspects . 8 10.4 VPN architectural aspects 8 10.5 VPN technical considerations 11 11 Guidelines for Product Selecti
11、on 12 11.1 Carrier protocol selection .12 11.2 VPN appliances 12 Bibliography .14BS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standard
12、ization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mu
13、tual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. International Standards are drafted in accord
14、ance with the rules given in the ISO/IEC Directives, Part 2. The main task of the joint technical committee is to prepare International Standards. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Stan
15、dard requires approval by at least 75 % of the national bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. ISO/IEC 27033
16、was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 27, IT security techniques. This first edition cancels and replaces ISO/IEC 18028-5:2006, which has been technically revised. ISO/IEC 27033 consists of the following parts, under the general title Inform
17、ation technology Security techniques Network security: Part 1: Overview and concepts Part 2: Guidelines for the design and implementation of network security Part 3: Reference networking scenarios Threats, design techniques and control issues Part 4: Securing communications between networks using se
18、curity gateways Part 5: Securing communications across networks using Virtual Private Networks (VPNs) Part 6: Securing wireless IP network access (Note that there may be other parts. Examples of possible topics to be covered by parts include local area networks, wide area networks, broadband network
19、s, web hosting, Internet email, and routed access to third-party organizations. The main clauses of all such parts should be Risks, Design Techniques, and Control Issues.)iv ISO/IEC 2013 All rights reservedBS ISO/IEC 27033-5:2013INTERNATIONAL ST ANDARD ISO/IEC 27033-5:2013(E) Information technology
20、Security techniques Network security Part 5: Securing communications across networks using Virtual Private Networks (VPNs) 1 Scope This part of ISO/IEC 27033 gives guidelines for the selection, implementation, and monitoring of the technical controls necessary to provide network security using Virtu
21、al Private Network (VPN) connections to interconnect networks and connect remote users to networks. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited
22、 applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 27001:2005, Information technology Security techniques Information security management systems Requirements ISO/IEC 27002:2005, Information technology Security techniques Code
23、of practice for information security management ISO/IEC 270 05:2011, Information technology Security techniques Information security risk management ISO/IEC 27033-1:2009, Information technology Security techniques Network security Part 1: Overview and concepts 3 T erms a nd definiti ons For the purp
24、oses of this document, the terms and definitions given in ISO/IEC 7498 (all parts), ISO/IEC 27000, ISO/IEC 27001, ISO/IEC 27002, ISO/IEC 27005, and ISO/IEC 27033-1 apply. ISO/IEC 2013 All rights reserved 1BS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) 4 Abbreviations For the purposes of this documen
25、t, the abbreviated terms given in ISO/IEC 27033-1 and the following apply. AH Authentication Header ESP Encapsulating Security Payload IKE Internet Key Exchange IPsec Internet Protocol Security ISAKMP Internet Security Association and Key Management Protocol L2F Layer Two Forwarding (Protocol) LDP L
26、abel Distribution Protocol MPPE Microsoft Point-to-Point Encryption MPLS Multi-protocol Label Switching NAS Network Area Storage OSI Open Systems Interconnection PPP Point-to-Point Protocol PPTP Point-to-Point Tunneling Protocol SSL Secure Sockets Layer VPLS Virtual Private LAN Service VPWS Virtual
27、Private Wire Service WAN Wide Area Network 5 Document structure The structure of ISO/IEC 27033-5 comprises: an overview of VPNs (see clause 6), security threats associated with VPNs (see clause 7), security requirements derived from threat analysis for VPNs (see clause 8), security controls associat
28、ed with typical network scenarios and network technology areas using VPNs (see clause 9), various design techniques for VPNs (see clause 10). 6 Overview 6.1 Introduction VPNs have developed rapidly as a means of inter-connecting networks and as a method of connecting remote users to networks.2 ISO/I
29、EC 2013 All rights reservedBS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) There exists a broad range of definitions for VPNs. In their simplest form, they provide a mechanism for establishing a secure data channel or channels over an existing network or point-to-point connection. They are assigned t
30、o the exclusive use of a restricted user group, and can be established and removed dynamically, as needed. The hosting network may be private or public. An example representation of a VPN, with the secure data channel connecting an end user to a gateway across a public network and a secure data chan
31、nel connecting two gateways across a public network, is shown in Figure 1 below. User Attacker 2 Attacker 1 Gateway VPN between User and Gateway Public Network Figure 1 Example representations of a VPN Remote access using a VPN is implemented over the top of a normal point-to-point connection. The n
32、ormal point-to-point connection between the local user and the remote locations is established first. Some VPNs are provided as a managed service, in which secure, reliable connectivity, management and addressing, equivalent to that on a private network, are provided on a shared infrastructure. Addi
33、tional security controls, as indicated in this standard, may therefore need to be taken into account to strengthen the VPN. The data and code transiting a VPN should be restricted to the organization using the VPN and should be kept separate from other users of the underlying network. It should not
34、be possible for data and code belonging to other users to access the same VPN channel. The level of trust in the confidentiality and other security aspects of the organization owning or providing the VPN should be taken into consideration when evaluating the extent of additional security controls th
35、at may be required. 6.2 Types of VPNs As stated above, there are multiple ways of expressing types of VPN. Architecturally, VPNs comprise of either: a single point-to-point connection (e.g. client device remotely accessing an organizations network via a site gateway, or a site gateway connecting to
36、another site gateway), or a point-to-cloud connection (e.g. implemented by MPLS technology). From an OSI Basic Reference Model perspective, there are three main types of VPN: Layer 2 VPNs offer a simulated LAN facility, using VPN connections running over a hosting network (e.g. a providers network)
37、to link sites of an organization or to provide a remote connection to an organization. Typical provider offerings in this area include Virtual Private Wire Service (VPWS), ISO/IEC 2013 All rights reserved 3BS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) which provides a simulated “wires only connecti
38、on”, or Virtual Private LAN Service (VPLS), which provides a more complete simulated LAN service. Layer 3 VPNs offer a simulated WAN facility, again using VPNs running over a network infrastructure. These offerings provide sites with simulated “OSI Network Layer” connectivity. A basic attraction her
39、e is the ability to use private IP addressing schemes over a public infrastructure, a practice that would not be permitted over a “normal” public IP connection. Whilst private addresses can be used over public networks via NAT (Network Address Translation), this can complicate IPsec VPN establishmen
40、t and use, although there are work-arounds available. Higher Layer VPNs are used for securing transactions across public networks. They typically provide a secure channel between communicating applications, thus ensuring data confidentiality and integrity during the transaction. This type may also b
41、e known as a Layer 4 VPN because the VPN connection is usually established over TCP which is a Layer 4 protocol. 7 Security Threats For the foreseeable future, organizations can expect increasingly sophisticated attacks to be mounted against their systems. Attempts at unauthorized access can be mali
42、cious, for example leading to a Denial- of-Service attack, the misuse of resources, or the access to valuable information. Generally speaking threats against a VPN can be in the form of Intrusions or Denial of Service (DoS). Intrusions happen when an outsider or malicious perpetrator takes control o
43、ver part of your network; this can be a computer or other networking device (including mobile devices). Intrusions may come from any location that has connectivity to your/the network. These attacks can come from other VPNs, the internet or the service provider core itself. The protection against th
44、ese types of attacks comes from the ability to filter unwanted traffic from unwanted sources on networks ingress points. One of the typical examples of intrusion is the unauthorized access to the secure tunnel by an unauthorized entity. This can be difficult in some VPN design models which lack cent
45、ralization as all sites connect to each other without traffic control. DoS attacks are another type of threat against a VPN. Both DoS attacks and intrusions can come from another VPN, the internet or the service provider core The main difference between the two types of attacks is that for DoS attac
46、ks the attacker needs to get access or have control over one of your pieces of equipment. DoS attacks against the service provider devices can also cause a denial of service to some parts of your VPN. Although it might be hard to sometimes protect your network against DoS attacks, the main protectio
47、n against them lies in the good network design of the VPN. Security issues for VPNs include: address space and routing separation between VPNs carried over the label switched network; ensuring that the internal structure of the label switched network core is not visible to outside networks (e.g. to
48、limit information available to a potential attacker); providing resistance to denial of service attacks; providing resistance to unauthorized access attacks; protecting against label spoofing (although whilst it may be possible to insert wrong labels into a label switched network from the outside, b
49、ecause of address separation the spoofed packet would only harm the VPN from which the spoofed packet originated).4 ISO/IEC 2013 All rights reservedBS ISO/IEC 27033-5:2013ISO/IEC 27033-5:2013(E) 8 Security Requirements 8.1 Overview The primary security objective of a VPN is protection from unauthorized access. VPNs could therefore be used to fulfill wider network security objectives: to safeguard information in networks, in systems connected to networks
