Individual Submission M McFadden
Internet Draft internet policy advisors ltd
Intended status: Informational August 16, 2021
Expires: February 16, 2022
Evolution of Endpoint Security - A Taxonomy for Endpoints
draft-mcfadden-opsec-endp-taxonomy-01
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Abstract
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A separate document [I-D:draft-mcfadden-opsec-endp-evolve] attempts
to establish the capabilities and limitations of endpoint-only
security solutions and explore potential alternative approaches.
That document discusses endpoints in general terms. It has been
suggested that there are classes of endpoints that have different
characteristics. Those classes may have completely different threat
landscapes and the endpoints may have completely different security
capabilities. As a companion to the endpoint evolution draft, this
document provides a taxonomy of endpoints that is intended to
provide a foundation for further work on endpoint security evolution
and research on approaches to providing endpoint security
alternatives in a diverse group of settings.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................3
3. Problem Statement..............................................4
4. The Endpoint in the EVOLVE draft...............................4
5. Taxonomy and Hierarchy.........................................5
6. Taxonomy.......................................................5
6.1. Traditional and Enterprise Computing Equipment [TECE].....6
6.1.1. Description..........................................6
6.1.2. Endpoint characteristics.............................6
6.2. Personal Computing Equipment..............................7
6.2.1. Description..........................................7
6.2.2. Endpoint characteristics.............................7
6.3. Human Interface Devices...................................8
6.3.1. Endpoint description.................................8
6.3.2. Endpoint characteristics.............................8
6.4. Human Sensor Devices......................................9
6.4.1. Endpoint characteristics............................10
6.5. Non-human Sensor Devices.................................10
6.5.1. Endpoint Description................................10
6.5.2. Endpoint characteristics............................11
6.6. Peripheral Computing Equipment and Embedded Endpoints....11
6.6.1. Endpoint Description................................11
6.6.2. Endpoint characteristics............................12
6.7. Application Layer Endpoints..............................12
6.7.1. Description.........................................12
6.7.2. Endpoint Characteristics............................13
6.8. Edge Network and Acquisition Endpoints...................13
6.8.1. Description.........................................13
6.8.2. Endpoint characteristics............................14
7. Security Considerations.......................................15
8. IANA Considerations...........................................15
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9. References....................................................15
9.1. Informative References ..................................15
10. Acknowledgments..............................................15
Appendix A. Document History.....................................17
1. Introduction
A document entitled "Evolution of Endpoint Security - An Operational
Perspective (EVOLVE) [I-D. draft-mcfadden-opsec-endp-evolve-00]
attempts to initiate research into the limits of endpoint-only
security solutions.
This draft attempts to suggest a Taxonomy of Endpoints as a
foundation for further work on the EVOLVE draft. The goal is to
identify classes of endpoints with similar characteristics. Those
characteristics may lead to the discovery that the devices in a
particular category share similar characteristics for endpoint
security.
It is essential to understand that this taxonomy is intended as a
foundation for work on the EVOLVE draft and is not an all-purpose
guide to the enormous breadth of devices that are or could be
endpoints on public or private networks. Others have attempted to
provide classifications for end devices, but they are not focused on
the issues related to endpoint security. In addition, most are
almost immediately out-of-date when published.
This document takes a different approach: the taxonomy here is
intended to support the work of the EVOLVE draft and provide a
classification system that may make it possible to group endpoints
in related categories for the purpose of discussing their security
characteristics. While a general-purpose taxonomy of Internet
endpoints might be useful in a variety of settings, it is not the
intended goal of this document.
In addition, this document does not attempt to assess and document
the endpoint security characteristics of each part of the taxonomy.
The work of identifying advantages and limitations of specific
classes of endpoints is envisioned as future work on the EVOLVE
draft.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. Problem Statement
The EVOLVE draft attempts to provide an analysis of the current
state of the provision of endpoint security. It does that by
providing a provisional definition of an endpoint and then examining
the advantages and limitations of providing security at that
endpoint.
The original approach to the EVOLVE draft divides the universe of
endpoints into User Equipment (UE) and hosts - and then focuses
entirely on User Equipment.
User Equipment encompasses a very broad set of endpoints. It may be
possible to provide a stronger set of device type groupings.
Endpoints in the same groups may share security characteristics that
are particular to that group. The fundamental question is: can a
taxonomy of endpoint devices be created that allows for grouping of
endpoints that have similar security characteristics?
If it is possible to answer that question in the affirmative, then
research can be done on the security characteristics of each
category and influence the development of protocols that have the
greatest impact for those type of devices.
4. The Endpoint in the EVOLVE draft
The EVOLVE draft simplifies the representation of an endpoint by
providing the following model:
+------------------------------------------------+
| |
| Application |
| |
|------------------------------------------------|
| |
| OS / Execution Environment |
| |
|------------------------------------------------|
| |
| Hardware |
| |
+------------------------------------------------+
Figure 1 Endpoint Generalization in the EVOLVE draft
This simplification means that there are many combinations of
hardware, operating systems, execution environments and
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applications. It also means that any of these three layers can be an
endpoint for the purposes of a discussion of endpoint security.
The EVOLVE draft suggests that we consider endpoints including those
which have a variety of power, computational, storage and network
capacities. It is possible that grouping devices with similar
characteristics will help in identifying categories of devices that
share similar endpoint security characteristics.
5. Taxonomy and Hierarchy
One suggestion for the taxonomy for endpoints is to consider a
hierarchy of endpoints that collects similar endpoint types in large
categories and then distinguishes between them in "sub-groups" or
lower levels of the taxonomy.
The advantage to using both the taxonomy and the EVOLVE draft is
that the groupings may provide a way to categorize threats and
mitigations to large classes of endpoints on the Internet while
providing the ability for differentiation. An example might be a
class of endpoints characterized as "constrained devices."
As an example, "constrained devices" might be further subdivided
into sub-classes such as sensors, embedded processors, specific (or,
special) purpose single-use processors, mesh gateways, and so forth.
It can even be imagined that the second level of the hierarchy could
be further subdivided by further distinguishing the endpoint types.
The current version of the draft does not take this approach. One of
the goals of the endpoint taxonomy is to provide enough
differentiation and specificity to ensure that a later version of
the EVOLVE draft can successfully discuss common threats and
mitigations for each of the categories in the taxonomy. By providing
an ever greater hierarchy of endpoint types, it becomes difficult to
scale the EVOLVE document that discusses threats and mitigations to
the highly specific endpoint types.
6. Taxonomy
Others have attempted to provide general-purpose taxonomy and device
classification guides (informative references to be provided in a
later draft version). In some settings automated detection and
classification of devices provides an essential step in providing
appropriate access control and security services.
General-purpose classification systems tend to ossify or become
enormously complex. Classification has come from commercial
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entities, computer science organizations, the academic community and
even regional collections of cooperating national governments.
For the purposes of providing a taxonomy for the EVOLVE draft, we
limit the discussion to a taxonomy for endpoints only. We divide
endpoints into eight different classes and then attempt to carefully
describe the characteristics of devices in each class.
6.1. Traditional and Enterprise Computing Equipment [TECE]
6.1.1. Description
Traditional and Enterprise Computing Equipment is characterized by
its extremely high-capacity for transactional volume, storage and
shared user population. TECE forms the backbone of high-volume,
high-availability transactional computing and is provided in both
physical and virtualized forms.
Traditional computing endpoints are shared computing environments
characterized by centralized, shared computing. These endpoints are
often in large scale data centers. These endpoints are capable of
high-availability, substantial requirements for power and
environmental control. These endpoints are also characterized by
very complex operating systems and user environments.
6.1.2. Endpoint characteristics
o Cost - these endpoints are characterized by extremely high cost.
o Physical size - these are very large endpoints, not suitable or
intended for use by an individual.
o Network link characteristics - capable of supporting extremely
high bandwidth.
o User interface - very complex and shared among multiple
individuals.
o Processing power - extremely high processing capability.
o Physical power - requires substantial provision of electrical
power and environmental controls.
o Code complexity - Extremely high support for very complex code
including parallelism, multitasking and multithreaded execution.
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6.2. Personal Computing Equipment
6.2.1. Description
These are endpoints designed or intended to be used by an
individual. They can be delivered as fixed, portable or virtual
instantiations of the endpoint. It should be noted that virtual
instantiations of endpoints introduce complexities in defining the
characteristics of the endpoints. In each case, the device supports
a mechanism for human-interface and has the capability for both
local storage and processing. The personal computing equipment class
is also characterized by relatively low cost and power requirements.
This class of endpoint is also characterized by the devices
supporting multiple purpose use. This class is divided into two
sub-classes: fixed and mobile endpoints. The mobile subclass is
further divided into four other subclasses: laptops, tablets,
intelligent phones, and ultraportable personal computing equipment.
Personal computing endpoints usually have at least one, and often
many, network links - often supporting a variety of network
connectivity technologies. These endpoints are also characterized
by having a human interface - either integral to the computing
device itself or supplied externally to the computing device.
6.2.2. Endpoint characteristics
o Cost - these endpoints have a huge range of costs, from extremely
inexpensive for simple "personal computer on a board" endpoints
to moderately expensive for specially configured laptop and fixed
devices.
o Physical size - the physical size of these devices range from
handheld to a small cabinet for fixed, desktop units.
o Network link characteristics - personal computing endpoints are
often characterized by supporting multiple connectivity
technologies.
o User interface - personal computing endpoints are characterized
by having user interfaces designed for an individual. The
interface varies from simple, text-based interaction to gesture,
touch and voice control.
o Processing power - these endpoints are characterized by a
significant range of processing power: from single CPU units to
endpoints that can support multiple concurrent processes.
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o Physical power - personal computing endpoints are characterized
by using either traditional mains power or power supplied by a
battery.
o Code complexity - personal computing endpoints support complex
code and often parallel and multithreaded execution of code.
6.3. Human Interface Devices
6.3.1. Endpoint description
Human interface transactions begin with a task-related goal for a
user. This leads to a user behavior (such as pointing, typing or
touching) which occurs in the current computing environment. The
user's action then should trigger an event in the current computing
environment.
Early computer science research breaks the taxonomy for Human
Interface Devices into four large categories: input devices,
pointing devices, indirect pointing and speech recognition. More
recent research adds neural interfaces, VR sensors, and human
attribute sensors. In all of these cases, the endpoints have the
goal of providing a mechanism for user navigation, interconnection,
form filling, menu interaction, data entry or sensing of human input
(although not to be confused with the following category in the
taxonomy). The result is that this category of the taxonomy has been
characterized by extremely limited computing capability in the past.
In contemporary networks the human interface devices are far more
complex and, as a result, subject to a wider collections of risks as
endpoints.
Since human interface devices are often the mechanism that provides
control of a computing resource, attacks on those devices are of
particular concern. In the past, the idea that there was an
external threat to a mouse or a pointing device would be ignored. In
contrast, today's voice actuated input devices and VR interfaces are
sophisticated enough to represent a real platform for attack.
6.3.2. Endpoint characteristics
o Cost - these endpoints are typically low in cost compared to
traditional computing equipment. They are often closer in cost to
simple peripheral equipment rather than endpoints that provide
general purpose computing platforms.
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o Physical size - these devices are meant to provide a human
interface and are sized appropriately to that use case. Examples
include those devices that are small enough to be handheld or
worn.
o Network link characteristics - human interface devices are
connected in a variety of ways. Early devices were wired to the
device to which they provided connectivity. More recently, these
devices have a network connection between them and the connected
device. Examples of this connection use Bluetooth or other, very
local network connections. These devices may have connections to
wider networks to support applications such as augmented reality.
o User interface - generally these devices provide a user interface
rather than having a distinct user interface of their own. More
complex human interface devices have limited interfaces for
settings and control of the device, and its connectivity and
function.
o Processing power - these devices are characterized by having
limited processing power.
o Physical power - most human interface devices are characterized
by having limited power requirements. They are sometimes powered
by their connection to the device. In other cases, they are
powered by a battery.
o Code complexity - human interface devices tend to have either no
or very limited capabilities to execute code. Modern interface
devices which support presentation of a virtual physical
environment are capable of executing the code needed to provide
the interface between the presentation of visual (and other)
stimuli while responding to gestures and movement of the person
using the device.
6.4. Human Sensor Devices
Description
These are endpoints whose primary purpose is to sense, store,
transmit or process information about a human being. These
endpoints are characterized as having use cases in health and
wellness monitoring, human performance enhancement, personalized
medicine and human safety.
The endpoints are characterized as sensor devices with the capacity
to sense, store and report on data collected on an individual. The
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sensor may be multimodal. These endpoints are almost always
characterized by have a battery for power and having limited
storage, networking and processing capabilities.
6.4.1. Endpoint characteristics
o Cost - Human Sensor Endpoints can range in cost from very low
(for instance a heartbeat sensor) to quite expensive (a sensor
built into an implanted device).
o Physical size - human sensors are very small and almost always
portable.
o Network link characteristics - human sensors usually have a
single network like technology available and are capable of very
limited bandwidth utilization on that link.
o User interface - human sensors have extremely limited, or no,
user interface.
o Processing power - human sensors are characterized by having
limited processing power - often incorporating only the ability
to collect store and forward sensed information.
o Physical power - human sensors are characterized by being powered
by internal batteries
o Code complexity - human sensors are not usually capable of
running complex code. Often, the capability of the endpoint is to
simply sense, store and forward data without reporting and
analysis of that data.
6.5. Non-human Sensor Devices
6.5.1. Endpoint Description
These endpoints are capable of sensing, storage, communication and
possibly some computation. They are characterized by having very low
bandwidth radios, a battery for power, sensor technology and a small
processor. Unlike in Section 5.4, these devices are not intended to
sense human-related information.
Compared with Human Sensors, non-human sensors often have a variety
of communications technologies available - for instance, self-
organizing into mesh networks.
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6.5.2. Endpoint characteristics
o Cost - Non-human Sensor Endpoints can range in cost from very low
(for instance, a simple temperature sensor) to quite expensive (a
sensor built into an implanted device.
o Physical size - Non-human sensors are often small and almost
always portable.
o Network link characteristics - Non-human sensors usually have a
single network like technology available but the topology of
those network links can be highly varied. Quite often these
devices are capable of very limited bandwidth utilization on the
link to which they are attached.
o User interface - non-human sensors have extremely limited, or no,
user interface.
o Processing power - non-human sensors are characterized by having
limited processing power - often incorporating only the ability
to collect store and forward sensed information. Some non-human
sensors have the capability to process stored data, but usually
this is limited.
o Physical power - non-human sensors often require very limited
amounts of power - very often provided by a battery.
o Code complexity - non-human sensors are not usually capable of
running complex code. Often, the capability of the endpoint is to
simply sense, store and forward data without reporting and
analysis of that data.
6.6. Peripheral Computing Equipment and Embedded Endpoints
6.6.1. Endpoint Description
These are endpoints that are "embedded" in devices that may have a
different primary function. An example is a network endpoint in a
printer that supports remote access, configuration and printing.
Another example is an endpoint in an appliance that has a different
primary function (for instance, a refrigerator).
In either case, the endpoint is characterized as being added to
another system, machine or peripheral.
These devices are characterized as being specialized for their
particular use case and function. Their specific characteristics
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often depend upon the system, device or peripheral in which they are
being hosted. As an example, the embedded endpoint gets its
physical power and networking capabilities from the device in which
it is connected.
6.6.2. Endpoint characteristics
o Cost - almost never available as a standalone device - instead,
always embedded into the peripheral or system which is hosting
it.
o Physical size - almost always very small - to be embedded into
some other system or device.
o Network link characteristics - dependent on network services
available from the host device and not always IP-based.
o User interface - almost always provided by the "hosting" device.
Many embedded endpoints share a user interface with the
configuration and control tool for the underlying device.
o Processing power - usually limited and constrained by the use
case. Some embedded endpoints provide remote access to the
underlying resources provided by the processor.
o Physical power - generally supplied by the "host" system or
device.
o Code complexity - limited and almost always constrained by use
case.
6.7. Application Layer Endpoints
6.7.1. Description
A significant trend in the contemporary public Internet is to have
applications act as completely independent agents - a situation
where the application itself provides the necessary infrastructure
(for instance, domain name resolution) to provide services. An
example would be a web browser that independently resolved domain
names and established secure communication channels independently.
The traffic between the application and the servers it uses might
not be available for analysis by security software. As a result,
application-based endpoints would have the characteristic of having
to provide security services (for instance, traffic security or
malware detection) for itself.
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This type of endpoint also has the characteristic of potentially
having adverse impacts on other applications running on the same
platform. For example, if several applications are provisioning
their own infrastructure services, then those services are being
duplicated on that platform. For security related infrastructure
there would be no common, platform-wide approach to securing the
applications or the traffic generated between the application and
external servers.
6.7.2. Endpoint Characteristics
o Cost - applications vary widely in cost and some are free.
o Physical size - based on code, application endpoints do not have
physical characteristics (e.g. size, power requirements, etc.).
o Network link characteristics - applications often use network
facilities provided by lower layers of the stack. In particular,
many application endpoints use the network services provided by
the underlying operating system that acts as the host for the
application. An emerging trend in both wired and wireless
networks is for the application to interface with the network
link to control or provide some of the network link services for
itself. An example of this would be an application that does DNS
resolution services for itself rather then depending on the
underlying operating system to provide that service.
o User interface - the application usually provides its own user
interface which can be minimal (for instance, command line
driven) or complex (windows or VR driven).
o Processing power - always dependent on the device on which the
application is hosted.
o Physical power - based on code, application endpoints do not have
physical requirements (e.g. power)
o Code complexity - highly variable. Applications can be very
simple or highly complex depending on the application's
requirements.
6.8. Edge Network and Acquisition Endpoints
6.8.1. Description
The emergence of intelligent devices and things has led to new
network designs where data is aggregated at points topologically
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close to where the data is gathered. The gathered data can then
have the option to flow to nearby gateways, or a Wi-Fi/W-LAN (SD-
WAN) router/equipment, or the telco tower/rooftop towers. These
often perform an acquisition function that includes both aggregation
and data condensation.
They usually have some level of processing capability. The main task
for these devices is to collect the data from various other
endpoints and send the processed data upstream. In doing so, they
often perform some low-level data processing, such as data filtering
(which determines what data is sent/blocked) and data analytics.
The acquisition systems are often architected to talk to distributed
data centers and end devices; for instance, on a factory shop floor,
a CDN's edge PoP (Point of Presence), an edge colocation local, or a
metro regional datacenter for a Telco or IT Service Provider.
In all cases, these edge computing devices represent a newer class
of endpoints. These are endpoints that are not at the extreme edge
of the network, but provide services to the devices at those edges
(especially for those devices in the class discussed in section 6.4
and 6.5 above).
The threats and mitigations for this class of device is expected to
be significantly different from those in sections 6.4 and 6.5.
6.8.2. Endpoint characteristics
o Cost - highly variable. Edge network devices in 5G networks can
be very expensive. Aggregation nodes in sensor networks can be
very inexpensive.
o Physical size - highly variable. Edge network devices in 5G
networks can be larger than personal computing equipment.
Aggregation nodes in sensor networks can be as small as a circuit
board, battery and radio.
o Network link characteristics - by their nature, these devices
have at least a pair of network links. One of these links faces
toward the network where the data is being aggregated. The other
faces toward the network where the data is being processed,
analyzed or reported upon.
o User interface - these devices usually have a limited user
interface, characterized by the need to configure the device,
provide security and allow for management of the network links.
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o Processing power - usually these devices have limited processing
power: their emphasis is on aggregation and management of data
flows between networks.
o Physical power - highly variable. Edge network devices in 5G
networks can require significant sources of secure and consistent
power. Aggregation nodes in sensor networks can often be
supported by a small battery.
o Code complexity - usually these devices have limited ability to
load and execute code. Since their emphasis is on aggregation and
management of data flows between networks, these devices usually
have minimal ability to run general purpose code.
7. Security Considerations
This draft is non-normative and simply attempts to provide a
taxonomy for endpoints. The goal of the taxonomy is to document that
there are classes of endpoints that have different characteristics.
Those classes may have completely different threat landscapes and
the endpoints may have completely different security capabilities.
In support of the work on the EVOLVE draft [I-D:draft-mcfadden-
opsec-endp-evolve-00], this draft provides a taxonomy of endpoints
that is intended to provide a foundation for further work on the
EVOLVE draft and research on approaches to providing endpoint
security alternatives in a diverse group of settings.
8. IANA Considerations
This memo contains no instructions or requests for IANA. The authors
continue to appreciate the efforts of IANA staff in support of the
IETF.
9. References
9.1. Informative References
[I-D. draft-mcfadden-opsec-endp-evolve-01], McFadden, M., "Evolution
of Endpoint Security - An Operational Perspective", Internet Draft
(work in progress), August 2021
10. Acknowledgments
The original idea for this draft came from another, now expired
draft. The authors of that draft intended a comprehensive
discussion of endpoint security and a clear description of how the
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evolution of the Internet made endpoint security - on its own -
insufficient.
The author thanks those previous contributors: Arnaud Taddei, Bret
Jordan, Candid Wueest, Chris Larsen, Andre Engel, Kevin Roundy,
Yugiong Sun, and David Wells.
The author also extends his appreciation to the discussions in the
IAB Activity called model-t where the future of the Internet's
threat landscape has also been discussed.
This document was prepared using 2-Word-v2.0.template.dot.
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Appendix A. Document History
[[ To be removed from the final document ]]
-00
Initial Internet Draft
-01
Minor editorial changes.
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Authors' Addresses
Mark McFadden
Internet policy advisors ltd uk
6 Bridge Street
Chepstow, Wales NP16 5EY
United Kingdom
Phone: +44 2921 25 3649
Email: mark@internetpolicyadvisors.com
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