Network Working Group I. Learmonth
Internet-Draft Tor Project
Intended status: Informational May 16, 2019
Expires: November 17, 2019
Guidelines for Performing Safe Measurement on the Internet
draft-learmonth-pearg-safe-internet-measurement-02
Abstract
Researchers from industry and academia will often use Internet
measurements as a part of their work. While these measurements can
give insight into the functioning and usage of the Internet, they can
come at the cost of user privacy. This document describes guidelines
for ensuring that such measurements can be carried out safely.
Note
Comments are solicited and should be addressed to the research
group's mailing list at pearg@irtf.org and/or the author(s).
The sources for this draft are at:
https://github.com/irl/draft-safe-internet-measurement
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 17, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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1. Introduction
When performing research using the Internet, as opposed to an
isolated testbed or simulation platform, means that you research co-
exists in a space with other users. This document outlines
guidelines for academic and industry researchers that might use the
Internet as part of scientific experiementation.
1.1. Scope of this document
Following the guidelines contained within this document is not a
substitute for any institutional ethics review process you may have,
although these guidelines could help to inform that process.
Similarly, these guidelines are not legal advice and local laws must
also be considered before starting any experiment that could have
adverse impacts on user privacy.
1.2. Active and passive measurements
Internet measurement studies can be broadly categorized into two
groups: active measurements and passive measurements. Active
measurements generate traffic. Performance measurements such as TCP
throughput testing [RFC6349] or functional measurements such as the
feature-dependent connectivity failure tests performed by
[PATHspider] both fall into this category. Performing passive
measurements requires existing traffic. Passive measurements can
help to inform new developments in Internet protocols but can also
carry risk.
The type of measurement is not truly binary and many studies will
include both active and passive components. Each of the
considerations in this document must be carefully considered for
their applicability regardless of the type of measurement.
2. Consent
Ideally, informed consent would be collected from all users of a
shared network before measurements were performed on them. In cases
where it is practical to do so, this should be done.
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For consent to be informed, all possible risks must be presented to
the users. The considerations in this document can be used to
provide a starting point although other risks may be present
depending on the nature of the measurements to be performed.
2.1. Proxy Consent
In cases where it is not practical to collect informed consent from
all users of a shared network, it may be possible to obtain proxy
consent. Proxy consent may be given by a network operator or
employer that would be more familiar with the expectations of users
of a network than the researcher.
2.2. Implied consent
In larger scale measurements, even proxy consent collection may not
be practical. In this case, implied consent may be presumed from
users for some measurements. Consider that users of a network will
have certain expectations of privacy and those expectations may not
align with the privacy guarantees offered by the technologies they
are using. As a thought experiment, consider how users might respond
if you asked for their informed consent for the measurements you'd
like to perform.
For example, the operator of a web server that is exposed to the
Internet hosting a popular website would have the expectation that it
may be included in surveys that look at supported protocols or
extensions but would not expect that attempts be made to degrade the
service with large numbers of simultaneous connections.
If practical, attempt to obtain informed consent or proxy consent
from a sample of users to better understand the expectations of other
users.
3. Safety Considerations
3.1. Use a testbed
Wherever possible, use a testbed. An isolated network means that
there are no other users sharing the infrastructure you are using for
your experiments.
When measuring performance, competing traffic can have negative
effects on the performance of your test traffic and so the testbed
approach can also produce more accurate and repeatable results than
experiments using the public Internet.
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WAN link conditions can be emulated through artificial delays and/or
packet loss using a tool like [netem]. Competing traffic can also be
emulated using traffic generators.
3.2. Only record your own traffic
When performing measurements be sure to only capture traffic that you
have generated. Traffic may be identified by IP ranges or by some
token that is unlikely to be used by other users.
Again, this can help to improve the accuracy and repeatability of
your experiment. [RFC2544], for performance benchmarking, requires
that any frames received that were not part of the test traffic are
discarded and not counted in the results.
3.3. Be respectful of other's infrastructure
If your experiment is designed to trigger a response from
infrastructure that is not your own, consider what the negative
consequences of that may be. At the very least your experiment will
consume bandwidth that may have to be paid for.
In more extreme circumstances, you could cause traffic to be
generated that causes legal trouble for the owner of that
infrastructure. The Internet is a global network crossing many legal
jurisdictions and so what may be legal for you is not necessarily
legal for everyone.
If you are sending a lot of traffic quickly, or otherwise generally
deviate from typical client behaviour, a network may identify this as
an attack which means that you will not be collecting results that
are representative of what a typical client would see.
3.3.1. Maintain a "Do Not Scan" list
When performing active measurements on a shared network, maintain a
list of hosts that you will never scan regardless of whether they
appear in your target lists. When developing tools for performing
active measurement, or traffic generation for use in a larger
measurement system, ensure that the tool will support the use of a
"Do Not Scan" list.
If complaints are made that request you do not generate traffic
towards a host or network, you must add that host or network to your
"Do Not Scan" list, even if no explanation is given or the request is
automated.
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You may ask the requester for their reasoning if it would be useful
to your experiment. This can also be an oppertunity to explain your
research and offer to share any results that may be of interest. If
you plan to share the reasoning when publishing your measurement
results, e.g. in an academic paper, you must seek consent for this
from the requester.
Be aware that in publishing your measurement results, it may be
possible to infer your "Do Not Scan" list from those results. For
example, if you measured a well-known list of popular websites then
it would be possible to correlate the results with that list to
determine which are missing.
3.4. Only collect data that is safe to make public
When deciding on the data to collect, assume that any data collected
might become public. There are many ways that this could happen,
through operation security mistakes or compulsion by a judicial
system.
3.5. Minimization
For all data collected, consider whether or not it is really needed.
3.6. Aggregation
When collecting data, consider if the granularity can be limited by
using bins or adding noise. XXX: Differential privacy.
3.7. Source Aggregation
Do this at the source, definitely do it before you write to disk.
[Tor.2017-04-001] presents a case-study on the in-memory statistics
in the software used by the Tor network, as an example.
4. Risk Analysis
The benefits should outweigh the risks. Consider auxiliary data
(e.g. third-party data sets) when assessing the risks.
5. Security Considerations
Take reasonable security precautions, e.g. about who has access to
your data sets or experimental systems.
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6. IANA Considerations
This document has no actions for IANA.
7. Acknowledgements
Many of these considerations are based on those from the
[TorSafetyBoard] adapted and generalised to be applied to Internet
research.
Other considerations are taken from the Menlo Report [MenloReport]
and its companion document [MenloReportCompanion].
8. Informative References
[MenloReport]
Dittrich, D. and E. Kenneally, "The Menlo Report: Ethical
Principles Guiding Information and Communication
Technology Research", August 2012,
<https://www.caida.org/publications/papers/2012/
menlo_report_actual_formatted/>.
[MenloReportCompanion]
Bailey, M., Dittrich, D., and E. Kenneally, "Applying
Ethical Principles to Information and Communication
Technology Research", October 2013,
<https://www.impactcybertrust.org/link_docs/
Menlo-Report-Companion.pdf>.
[netem] Stephen, H., "Network emulation with NetEm", April 2005.
[PATHspider]
Learmonth, I., Trammell, B., Kuehlewind, M., and G.
Fairhurst, "PATHspider: A tool for active measurement of
path transparency", DOI 10.1145/2959424.2959441, July
2016,
<https://dl.acm.org/citation.cfm?doid=2959424.2959441>.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544,
DOI 10.17487/RFC2544, March 1999,
<https://www.rfc-editor.org/info/rfc2544>.
[RFC6349] Constantine, B., Forget, G., Geib, R., and R. Schrage,
"Framework for TCP Throughput Testing", RFC 6349,
DOI 10.17487/RFC6349, August 2011,
<https://www.rfc-editor.org/info/rfc6349>.
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[Tor.2017-04-001]
Herm, K., "Privacy analysis of Tor's in-memory
statistics", Tor Tech Report 2017-04-001, April 2017,
<https://research.torproject.org/techreports/
privacy-in-memory-2017-04-28.pdf>.
[TorSafetyBoard]
Tor Project, "Tor Research Safety Board",
<https://research.torproject.org/safetyboard/>.
Author's Address
Iain R. Learmonth
Tor Project
Email: irl@torproject.org
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