# Network measurements
This section of the magma guide discusses network measurement: the process of measuring specific types of network activity to determine if there is any interference or abnormality occurring on a particular network. The first several subsections below detail the various types of network measurements that can be performed, the hardware needed to conduct them, and the vantage points from where they will need to be conducted. The final subsections lay out network measurement best practices, associated risks, relevant ethical considerations, and volunteering considerations.
# Types of network measurements
Over the years a number of different methodologies have been developed to detect filtering/blocking of network resources, tampering with communication channels, and intentional manipulation of network routes. These types of methodologies can be categorized as either passive or active, depending on how they are deployed.
# Active/passive network measurements
Most network measurement techniques rely on passive detection methods that can be performed automatically from anywhere. Such techniques typically visualize a small subset of potential Internet censorship events within specific networks, countries, or geographic areas. Because the results from these techniques usually come from a limited number of vantage points (sample), they often provide an limited view of the actual Internet censorship landscape. Still, these techniques can be helpful when there is already evidence of an Internet censorship event occurring in a specific network segment or region, but the existing data are not enough to generalize about the nature, methods, and incentives behind the censorship activity.
Active detection methods are network measurements that are performed manually by either an entity or an individual. This type of network measurement typically provides a more precise understanding of the actual network filtering or content blocking that is occurring within a specific network segment. Due to their “active” nature these measurements are more challenging to conduct because they must be deployed from vantage points that either have access to, or are located within, the underlying network being measured. Note, however, that when active network measurements are deployed from vantage points outside the investigated network, their results do not always represent an accurate view of the network anomalies.
# Other network measurements
- Measurements to detect internet censorship, information controls, or other types of network filtering (e.g.: VPNs, anonymity networks).
- Measurements to detect network throttling, net neutrality, data discrimination, or alternated content based on geographical location.
Several types of hardware can be enlisted to perform network measurements, most notably mobile phones and stationary hardware devices.
# Mobile phones
Mobile phone is the most accessible and user-friendly type of hardware that can be used to perform network measurements. With access to a single phone, a user can perform network measurements from a variety of different networks by changing and connecting to other networks (either by mobile or with the use of SIM cards from various mobile operators).
But certain difficulties and concerns arise from using a mobile phone to conduct network measurements. It can be challenging to orchestrate and perform longitudinal (periodic) network measurements with a mobile phone as doing so requires physical attendance and manual instrumentation of network measurements. In addition, the device’s mobility can also present problems as its very nature makes the device more prone to failures and possible errors in network measurements. Battery and storage capacity are also limiting factors that can affect the successful completion and collection of data when using a mobile phone.
Mobile phone users should be aware that they can be easily tracked and identified by service providers, governments, and law enforcement agencies. Depending on a user’s threat model, a heightened degree of attention may be required when performing Internet censorship or surveillance related network measurements on a phone.
# Stationary hardware devices
Stationary hardware devices, such as desktop computers, servers, or embedded devices, can be utilized to perform uninterrupted as well as longitudinal (periodic) network measurements. These devices can be set up to require minimal or almost no physical attendance when conducting network measurements. Depending on the connection type, network bandwidth is typically not a limiting factor when using these devices. They also have greater storage capacity than mobile phones and can often operate uninterrupted to collect and store network measurements.
Trade-offs still exist, however, when using stationary hardware devices. Due to their fixed position, it is difficult to interchange, connect, and perform network measurements on different networks. Associated risks typically pertain to Internet access connection types and subscription plans.
# Vantage points
In order to achieve an accurate view of the Internet censorship activity in a specific area, access to vantage points from network(s) within the area is required. Vantage points can either be geographically bound or accessed remotely.
You should always ask for permission to use a specific network or vantage point for network measurements or any network related research (see the ISP inquiry template below). Always review the terms of service and acceptable usage policy of any given subscription plan or network.
# Geographically bound
Geographically bound vantage points, such as broadband services and mobile data connections, require "physical access" to a network (either the user or the equipment being used must be physically located within the network area being measured). Although this isn't always easy to achieve, such vantage points are particularly important for research purposes because they are often operated by local or regional ISPs which are known to implement extensive network filtering practices and surveillance tactics.
The use of geographically bound vantage points involves a higher level of risk for researchers because they usually must operate under their own names where the network connection is being provided.
# Remote access
Remote access type vantage points refer to networks that can be accessed remotely (for instance via a secure shell network service or via remote desktop services). Access to these networks can be granted by purchasing a subscription plan and does not require that the user or the equipment be physically located within the network area. Prices, availability, and plans vary based on geographic location, network bandwidth, and server technical specifications (storage capacity and computing power).
The use of remote access vantage points involves a lower level of risk factor for researchers because the only identifying information tied to the user is the payment information (if applicable) and the location of the connection to the VPN. Both identifiers can be pseudo-anonymized to increase user privacy and lower risk.
A VPN (Virtual Private Network) is (a tunneled) connection to a network that routes all network traffic to that network. VPNs can be used to conceal a user’s true network or access restricted internal services within a network. This type of vantage point offers access to many different networks in many different countries. It’s also typically low cost and easy to use. Although VPNs provide access to different vantage point locations, the VPNs themselves are usually not subject to information controls or other network blocking restrictions (note, however, that the real locations of various VPNs are not always marketed accurately).
- Razaghpanah, Abbas & Li, Anke & Filastò, Arturo & Nithyanand, Rishab & Ververis, Vasilis & Scott, Will & Gill, Phillipa. (2016). Exploring the Design Space of Longitudinal Censorship Measurement Platforms. Archived PDF version
- VPNs are Using Fake Server Locations, Sven Taylor
- Zachary Weinberg, Shinyoung Cho, Nicolas Christin, Vyas Sekar, and Phillipa Gill. 2018. How to Catch when Proxies Lie: Verifying the Physical Locations of Network Proxies with Active Geolocation. In 2018 Internet Measurement Conference (IMC ’18), October 31November 2, 2018, Boston, MA, USA. ACM, New York, NY, USA, 15 pages. https://doi.org/10.1145/3278532.3278551 Archived PDF version
Many different types of servers exist across the world, from bare metal dedicated servers to VPSes (Virtual Private Servers). In addition, users can rent a collocation facility to provide the space, power, network connectivity, storage, and physical security needed to host a server or other equipment.
Servers are often located in business networks or networks that do not otherwise employ the same network filtering and surveillance infrastructure found in geographically bound networks. Costs associated with the lease of server and rental of network bandwidth or other services can be a limiting factor, especially in locations where datacenter availability and network bandwidth are scarce.
# Vantage points comparison
|Connection Type||Risk Factor||Cost||Efficiency|
|Broadband||High||Low - Medium||High|
|Collocation||Low||High||Low - Medium|
|Dedicated Server||Low||High||Low - Medium|
|Mobile Broadband||High||Medium - High||High|
|VPN||Low||Very Low - Low||Very Low|
|VPS||Low||Low - Medium||Low - Mid|
# Server inquiry template
This following is a sample ISP inquiry template, which can be personalized and sent to an ISP to request permission to use a server to conduct network measurements:
Hi XXX, I am interested in your XXX server for performing network measurements. We are a registered association/research institution in City XXX. We are conducting Internet censorship research on the country/area XXX. Our research project is: XXX // Explain the purpose and scope of the research here \\ Are you fine with running network measurements from your network/server? We would be able to pay for XXX months up front or work on other billings/subscription plan. If you want to chat about it, you can find me on XXX. Thank you for your time. Kind regards, XXX
# List of ISPs in various locations
- ExoticVM - A list of all hosts offering VPSes in various geographic locations.
- LowEndTalk - A forum to request and view server offers in various geographic locations and lower prices.
- Web Hosting Talk - One of the largest web hosting communities, with offers and discussions about servers in different locations.
# Network measurements best practices
The following list of network measurement best practices has been drawn verbatim from Zmap's scanning best practices. Users preparing to conduct measurements should review this list (and Zmap’s website) prior to beginning their research.
When conducting network measurement, you should:
- Coordinate closely with local network administrators to reduce risks and handle inquiries
- Verify that network measurements will not overwhelm the local network or upstream provider
- Signal the benign nature of the network measurements in web pages and DNS entries of the source addresses Clearly explain the purpose and scope of the network measurements in all communications
- Provide a simple means of opting out and honor requests promptly
- Conduct network measurements no larger or more frequent than is necessary for research objectives
- Spread network measurements traffic over time or source addresses when feasible
In addition, network measurement researchers should do their best to comply with all jurisdictional legal requirements and avoid accessing otherwise protected resources on the web.
Please Note: An overview of privacy risks and risks related to the use of a specific tool or software can be found in the Performing network measurements section.
The risks and ethical considerations discussed below are drawn from the following article (available to read in Archived PDF version):
Zevenbergen, B., Brown, I., Wright, J., Erdos, D.O. (2013) Ethical Privacy Guidelines for Mobile Connectivity Measurements. Oxford Internet Institute, University of Oxford.
Researchers should be advised that conducting network measurements can impact the privacy of other Internet users, especially if specific data on user behavior is collected during the process. Once a dataset is disclosed online (either accidentally or not), researchers lose control over how these data will be used. Potentially sensitive data that has been collected as part of the network measurement process can cause harm to other individuals if they are identified as the result of a dataset disclosure.
Accordingly, any person conducting Internet censorship or surveillance related research should do their best to protect the personally identifiable information (PII) of third-party users. All research designs should be carefully reviewed, and efforts should be made to quantify the privacy and utility trade-offs from a risk perspective. The protection of personal information must be considered at all times to ensure privacy by design. A privacy impact assessment (PIA) should be prepared, detailing how personal information will be handled during the research project. The PIA should address legal, regulatory, ethical privacy requirements. A detailed examination and evaluation of technical safeguards and protections for handling information to mitigate potential privacy risks (such as evaluating the effectiveness of an anonymization technique) should be included, as should a plan to deal with the unforeseen disclosures of datasets.
# Assessing privacy risks
Prior to assessing privacy risks, researchers should be familiar with the following terms (the definitions below are drawn verbatim from Zevenbergen, et al.):
# Key definitions
A dataset is a collection of related sets of information that is composed of separate elements. The elements of datasets discussed in this framework are divided into three categories: (1) identifiers, (2) key attributes, and (3) secondary attributes.
- Identifiers are attributes that can individually distinguish the data subject more or less directly. Typical identifiers include: name, address, social security numbers, mobile phone number, IMEI number.
- Key attributes can be used to identity a data subject using auxiliary sources of information, by linking to databases that contain identifying information. They are indirect identifiers of a data subject, which make an individual more distinctive in a population. Typical key attributes include: age, race, gender, date of birth and place of residence.
- Secondary attributes cannot individually identify a data subject directly and may require significant amounts of auxiliary data to be useful for re identification purposes. A data subject may then be identified individually through more sophisticated methods such as fingerprinting, rather than mere linking of databases. Examples include the settings in an application, the battery level measured over time, or location patterns.
# Collection of data
Prior to collecting data, a full risk assessment should be performed to assess the relevant balance of risks and benefits. To properly manage privacy risks, researchers should know which data categories are required for their research, as well as how they will be collected and processed. Only relevant and non-excessive data should be collected (data minimization).
# Categorization of data types
Many types of data can be collected via network measurements. Researchers should be aware of each type of data they are collecting. “Identifiers” will directly identify the user. “Key attributes” will make a re-identification of the user possible/likely with only a few extra pieces of auxiliary data. “Secondary attributes” will need to be combined with several other data to re-identify the user through methods such as fingerprinting.
Below is a list of the various types of potentially PII data that can be collected when conducting network measurements. Researchers should be aware of the incumbent risks associated with collecting each type of data.
Privacy risks increase when more data types are collected because doing so increases the likelihood that inferences can/will be drawn. The data labels described above and used below (identifier, key-attribute, and secondary-attribute) are intended to be used only as general guidance. They will not be correct in all contexts. Researchers conducting relevant work should discuss any data categorization issues/labels in detail with colleagues and/or a legal expert.
# IMEI number
An IMEI number is the serial number of a phone, and is unique to each device. IMEI numbers do not directly identify a person (only a device), but because devices are generally owned and used solely by a specific individual, these numbers should be considered a key-attribute. Auxiliary data, such as billing information from the telecom operator, can identify that device’s owner or user.
# Current IP address
IP addresses identify devices participating in a computer network that uses the Internet Protocol for communication. Internet service providers and telecom operators may keep logs of IP addresses that are assigned to certain fixed line broadband connections. IP addresses for mobile devices, however, tend to be shared amongst multiple devices over time. It is frequently stated that mobile carriers do not keep accurate logs of which IP-addresses were assigned to which device at a given moment in time. This would make such data a secondary attribute. Under certain laws and policies, however, carriers are required to store data such as assigned IP addresses for specified periods of time, sometimes many years (although this can be complicated by common techniques such as Network Address Translation that allows multiple devices to share a single IP address). In case IP address logs do uniquely identify devices, IP addresses should be considered key-attributes that render a data subject identifiable.
# Name of carrier
Relatively few mobile carriers exist in the United States, with subscriber numbers ranging into the tens or hundreds of millions per carrier. Worldwide, however, there are many carriers with far fewer subscribers. This is especially true in places like Europe, where carriers exist that only have a few thousand subscribers. The name of the carrier will likely only be a secondary attribute, but the amount of auxiliary data required to identify a person will depend on the size and type of carrier. The name of an obscure carrier could be the necessary data point that allows a subscriber to be identified individually along with other attributes.
# Battery level
The current battery level of a mobile device is largely considered to be irrelevant for the identifiability of a mobile phone user. However, the rate of decay of battery power of devices, when monitored over time, can allow for differences to be found. While this type of monitoring would require significant analysis, it is not beyond the bounds of possibility (and may be made possible due to the perceived low sensitivity of gathering and releasing such data). Similarly, research has indicated that it is possible to identify many Internet users by analyzing their browser configurations (so far only proven on desktops). In sum, this is a good reminder that seemingly irrelevant data types can become key pieces in a larger re-identification scheme.
A GPS location gives an accurate position of a device. Locations of mobile phones can also be collected when the GPS is switched off, by triangulating the position with regards to Wi-Fi access points or cell towers. When a mobile phone moves, it is usually in the direct possession of a person (typically its owner). GPS or triangulated locations can therefore reveal the location of a specific person at a certain time and, more importantly, the series of locations through which the device and its owner have moved over time. Identifiability is very dependent on the context of the geographic location and the local population density. GPS location may not be a key-attribute, but research has shown that human mobility traces are highly unique.
# Other types
Other types of potentially PII that can be collected during network measurements include:
- Bearer information
- Caller ID
- Current DNS resolver
- Current memory usage
- Download throughput
- How many applications are running
- IMSI (International mobile subscriber identity)
- Identify active radio antenna
- Names of installed applications
- Operation system & version
- Upload throughput
- Visible networks
Narseo Vallina-Rodriguez, Srikanth Sundaresan, Christian Kreibich, and Vern Paxson. 2015. Header Enrichment or ISP Enrichment?: Emerging Privacy Threats in Mobile Networks. In Proceedings of the 2015 ACM SIGCOMM Workshop on Hot Topics in Middleboxes and Network Function Virtualization (HotMiddlebox '15). ACM, New York, NY, USA, 25-30. DOI=http://dx.doi.org/10.1145/2785989.2786002 Archived PDF version
Mulliner, Collin. (2010). Privacy leaks in mobile phone internet access. 10.1109/ICIN.2010.5640939. Archived PDF version
Prior to conducting network measurements, all researchers should be aware of the ethical considerations that accompany this type of work for both themselves and those that collect measurements on the ground. This is particularly important when enlisting volunteers to collect active network measurements that may bring them in potential danger.
Networked Systems Ethics helps researchers, engineers, and other interested parties create better ethical guidelines that consider divergences in social contexts, acknowledge personal knowledge shortcomings, and assess the expected impact of research in targeted areas or countries.
# Iterative Reflexivity Methodology
The iterative reflexivity methodology flowchart below provides a helpful overview of the fundamental considerations for ethical research designs.
Researchers and engineers can also use the following questions to help guide their ethical research design. These questions (and the info provided in the accompanying links) are a good way for users to identify potential gaps in their design or determine where more attention may be required (Source: Networked Systems Ethics - Summary questions (TL;DR)):
- Context: How would you describe the context within which data is collected, information flows are created (or affected), or phenomena are measured?
- Aims: What are the aim and benefits of the project?
- Benefits: Why are the benefits good for stakeholders?
- Purpose limitation: Can the scope of data collection be limited whilst still achieving the project aim?
- Politics and Power: Are particular stakeholders empowered or disempowered as a result of this project?
- Risk of Harm: Could the collection of the data in this study be reasonably expected to cause tangible harm to any person’s well-being?
- Law: Which bodies of law are likely to be applicable to the operation of the project?
- Values: Which values will the project conceivable impact?
- Burdens: Who carries the burden of harms or impacted values, and how?
- Technology Ethics: Can the harms and impacted values be traced to parts of the technological design of the project?
- Function Creep: Does the project potentially set a precedent for unethical methodologies that could be misused by others in the future?
- Data Governance: Using current techniques, can the data used in this study reveal private or confidential information about individuals?
- Data Retention: When will the collected data be deleted?
- Tech Alternatives: Have you considered measures to mitigate the identified risk of harm or impacted values?
- Limit Scope: Can you limit the scope of the project (geography, knowledge generated, etc.)?
- Methodology: Have others used alternative methodologies to achieve similar ends?
- Informed Consent: Do you need to rely on informed consent from participants and stakeholders?
# Further related work
Ethics and Internet Measurements. / van der Ham, Jeroen; van Rijswijk, Roland M. In: Journal of Cyber Security and Mobility, Vol. 5, No. 4, 3, 10.2017, p. 287-308. Archived PDF version
Zevenbergen, Bendert and Mittelstadt, Brent and Véliz, Carissa and Detweiler, Christian and Cath, Corinne and Savulescu, Julian and Whittaker, Meredith, Philosophy Meets Internet Engineering: Ethics in Networked Systems Research. (GTC Workshop Outcomes Paper) (September 29, 2015). Available at SSRN: https://ssrn.com/abstract=2666934 or http://dx.doi.org/10.2139/ssrn.2666934 Archived PDF version
This section provides considerations for individuals or groups (entities) who are interested in volunteering with a research project by performing network measurements, hosting the infrastructure, or assisting with crowd-sourcing activities.
Prior to volunteering or otherwise participating in network measurement research, you should seek advice from a legal entity within your country or jurisdiction to receive general advice and best assess the applicable laws and regulations.
Before you volunteer, you should review the relevant sections of the magma guide on Risks and Ethics to assess potential threats and minimize risk. In addition, it is important to create a threat model and map out any potential dangers. Further examples of volunteering best practices include:
- Establishment of close relationships with local people and civil society
- Obtaining advice from local communities and trusted entities
- Open methodologies review
- Does the project you are volunteering with provide open and clear methodologies?
- How does the software perform network measurements?
- Are there any data collected, and if so do they contain any PII information (see also Risks: Collection of data)
- Data retention: How long are the data kept?
- Request a detailed and honest consent form (see section Risks)
It is important to remember that types of network measurements may be also harmful in the future even if they are not (directly) associated with research related to Internet censorship or surveillance. For example, network speed tests (where users from various networks and endpoints are testing the quality of their network connection by measuring the link latency, download speed, and upload speed) are not entirely benign as many individuals suspect. Instead, these types of network measurements can be considered as harmless or to a much lesser degree risky. However such network measurements may be used to detect bandwidth throttling that can be used as a mechanism of Internet censorship. By slowing down the connection speed to a very low rate, Internet connectivity can be deemed unusable, especially for the distribution and usage of media content. Interested users can find out more about this research by reading: Dimming the Internet: Detecting Throttling as a Mechanism of Censorship in Iran by Collin Anderson.
"Notably, a government has multiple options to gather information about its citizens. It has technical powers to conduct surveillance through several state institutions like the police and intelligence agencies. It also has legal means to get data from companies like the internet service providers (ISPs), email providers, and social media platforms." Source: Reporters without Borders - Thread modulator