IPv4 and IPv6 Greynets
RFC 6018

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Internet Engineering Task Force (IETF)                          F. Baker
Request for Comments: 6018                                 Cisco Systems
Category: Informational                                        W. Harrop
ISSN: 2070-1721                                              G. Armitage
                                      Swinburne University of Technology
                                                          September 2010

                         IPv4 and IPv6 Greynets

Abstract

   This note discusses a feature to support building Greynets for IPv4
   and IPv6.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6018.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
     1.1.  History and Experience  . . . . . . . . . . . . . . . . . . 3
   2.  Deploying Greynets  . . . . . . . . . . . . . . . . . . . . . . 4
     2.1.  Deployment Using Routing - Darknets . . . . . . . . . . . . 4
     2.2.  Deployment Using Sparse Address Space - Greynets  . . . . . 4
     2.3.  Other Filters . . . . . . . . . . . . . . . . . . . . . . . 6
   3.  Implications for Router Design  . . . . . . . . . . . . . . . . 6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 8

1.  Introduction

   Darknets, also called "Network Telescopes" among other things, have
   been deployed by several organizations (including CAIDA, Team Cymru,
   and the University of Michigan) to look at traffic directed to
   addresses in blocks that are not in actual use.  Such traffic becomes
   visible by either direct capture (it is routed to a collector) or by
   virtue of its backscatter (its resulting in ICMP traffic or
   transport-layer resets).

   Darknets, of course, have two problems.  As their address spaces
   become known, attackers stop probing them, so they are less
   effective.  Also, the administrators of those prefixes are pressured
   by Regional Internet Registry (RIR) policy and business requirements
   to deploy them in active networks.

   [Harrop] defines a 'Greynet' by extension, in these words:

      Darknets are often proposed to monitor for anomalous, externally
      sourced traffic, and require large, contiguous blocks of unused IP
      addresses - not always feasible for enterprise network operators.
      We introduce and evaluate the Greynet - a region of IP address
      space that is sparsely populated with "darknet" addresses
      interspersed with active (or "lit") IP addresses.  Based on a
      small sample of traffic collected within a university campus
      network we saw that relatively sparse greynets can achieve useful
      levels of network scan detection.

   In other words, instead of setting aside prefixes that an attacker
   might attempt to probe and in so doing court discovery, Harrop
   proposed that individual (or small groups of adjacent) addresses in
   subnets be set aside for the purpose, using different host
   identifiers in each subnet to make it more difficult for an address

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   scan to detect them.  The concept has value in the sense that it is