[ISN] ITL Bulletin for June 2009

From: InfoSec News <alerts_at_private>
Date: Thu, 25 Jun 2009 02:46:46 -0500 (CDT)
Forwarded from: "Lennon, Elizabeth B." <elizabeth.lennon (at) nist.gov>



Karen Scarfone, Editor
Computer Security Division
Information Technology Laboratory
National Institute of Standards and Technology
U.S. Department of Commerce

Many people telework (also known as telecommuting), which is the ability 
for an organization's employees and contractors to perform work from 
locations other than the organization's facilities. Teleworkers use 
various client devices, such as desktop and laptop computers, cell 
phones, and personal digital assistants (PDAs), to read and send email, 
access Web sites, review and edit documents, and perform many other 
tasks. Most teleworkers use remote access, which is the ability for an 
organization's users to access its non-public computing resources from 
external locations other than the organization's facilities.

The Information Technology Laboratory of the National Institute of 
Standards and Technology (NIST) recently updated its guidelines on 
telework and remote access to help organizations protect their IT 
systems and information from the security risks that accompany the use 
of telework and remote access technologies. The revised guidelines 
discuss the technology, the current security risks involved in its use, 
and the recommended security solutions.

NIST Special Publication (SP) 800-46 Revision 1, Guide to Enterprise 
Telework and Remote Access Security: Recommendations of the National 
Institute of Standards and Technology

NIST SP 800-46 Revision 1, Guide to Enterprise Telework and Remote 
Access Security, written by Karen Scarfone and Murugiah Souppaya of 
NIST, and Paul Hoffman of the VPN Consortium, was issued in June 2009. 
It is a complete rewrite of the original NIST SP 800-46, Security for 
Telecommuting and Broadband Communications, which was released in August 

The new guidelines discuss the technical and physical vulnerabilities 
and threats against enterprise telework and remote access solutions. One 
section of the publication presents recommendations for securing remote 
access solutions, while another section focuses specifically on 
protecting telework client devices and their data. The last section of 
the guide discusses security throughout the telework and remote access 
life cycle.

NIST SP 800-46 Revision 1 contains an extensive list of references to 
online sources of information about telework and remote access security. 
The appendices include a glossary of the technical terms employed in the 
publication and an acronym list. NIST SP 800-46 Revision 1 is available 
from the NIST Web site:


Remote Access Methods

Organizations have many options for providing remote access to their 
computing resources. In NIST SP 800-46 Revision 1, the remote access 
methods most commonly used for teleworkers are divided into four 
categories based on their high-level architectures: tunneling, portals, 
remote desktop access, and direct application access.

Tunneling involves establishing a secure communications tunnel between a 
telework client device and a remote access server, often a virtual 
private network (VPN) gateway. The tunnel uses cryptography to protect 
the confidentiality and integrity of the communications. Application 
software on the client device, such as email clients and Web browsers, 
can communicate securely through the tunnel with servers within the 
organization. Tunnels can also authenticate users and restrict access, 
such as limiting which systems a telework client device can connect to.

A portal is a server that offers access to one or more applications 
through a single centralized interface. A teleworker uses a portal 
client on a telework client device to access the portal. Most portals 
are Web-based-for them, the portal client is a regular Web browser. The 
application client software is installed on the portal server, and it 
communicates with application server software on servers within the 
organization. The portal protects communications between the client 
devices and the portal, and portals can also authenticate users and 
restrict access to the organization's internal resources.

A remote desktop access solution gives a teleworker the ability to 
remotely control a particular desktop computer at the organization, most 
often the user's own computer at the organization's office, from a 
telework client device. The teleworker has keyboard and mouse control 
over the remote computer and sees that computer's screen on the local 
telework client device's screen. Remote desktop access allows the user 
to access all of the applications, data, and other resources that are 
normally available from their computer in the office.

With direct application access, remote access is accomplished without 
using remote access software. A teleworker can access an individual 
application directly, with the application providing its own security 
(communications encryption, user authentication, etc.) One of the most 
common examples of direct application access is Web-based access to 
email, also known as Webmail The teleworker runs a Web browser and 
connects to a Web server that provides email access. The Web server runs 
HTTP over SSL (HTTPS) to protect the communications, and the Webmail 
application on the server authenticates the teleworker before granting 
access to the teleworker's email.

Security Concerns

Telework and remote access technologies often need additional protection 
because their nature generally places them at higher exposure to 
external threats than technologies only accessed from inside the 
organization. Major security concerns for telework and remote access 
technologies include the following:

Lack of physical security controls is an issue because telework client 
devices are used in a variety of locations outside the organization's 
control, such as employees' homes, coffee shops, hotels, and 
conferences. The mobile nature of these devices makes them likely to be 
lost or stolen, which places the data on the devices at increased risk 
of compromise. Malicious parties may attempt to recover sensitive data 
from the devices. Even if a client device is always in the possession of 
its owner, there are other physical security risks, such as an attacker 
looking over a teleworker's shoulder at a coffee shop and viewing 
sensitive data on the client device's screen.

Unsecured networks are frequently used for remote access. Because nearly 
all remote access occurs over the Internet, organizations normally have 
no control over the security of the external networks used by telework 
clients. Communications systems used for remote access include telephone 
and Digital Subscriber Line (DSL) modems, broadband networks such as 
cable, and wireless mechanisms such as IEEE 802.11, WiMAX, and cellular 
networks. Attackers may eavesdrop on sensitive information, as well as 
intercepting and modifying communications.

Client devices infected with malware pose risks not only to the devices' 
data, but to other systems within the organization. Telework client 
devices, particularly laptops, are often used on external networks and 
then brought into the organization and attached directly to the 
organization's internal networks. If a client device is infected with 
malware, this malware may spread throughout the organization once the 
client device is connected to the internal network.

Providing remote access to internal resources such as servers may place 
them at additional risk. If these internal resources were not previously 
accessible from external networks, making them available via remote 
access will expose them to new threats, particularly from untrusted 
client devices and networks, and significantly increase the likelihood 
that they will be compromised. Each form of remote access that can be 
used to access an internal resource increases the risk of that resource 
being compromised.

NIST's Recommendations for Improving the Security of Telework and Remote 
Access Solutions

All the components of telework and remote access solutions, including 
client devices, remote access servers, and internal resources accessed 
through remote access, should be secured against expected threats, as 
identified through threat models.

NIST recommends that organizations apply the following safeguards to 
improve the security of their telework and remote access technologies:

Plan telework security policies and controls based on the assumption 
that external environments contain hostile threats.

An organization should assume that external facilities, networks, and 
devices contain hostile threats that will attempt to gain access to the 
organization's data and resources. Organizations should assume that 
telework client devices, which are used in a variety of external 
locations and are particularly prone to loss or theft, will be acquired 
by malicious parties who will attempt to recover sensitive data from 
them. Options for mitigating this type of threat include encrypting the 
device's storage and not storing sensitive data on client devices.

Organizations should also assume that communications on external 
networks, which are outside the organization's control, are susceptible 
to eavesdropping, interception, and modification. This type of threat 
can be mitigated, but not eliminated, by using encryption technologies 
to protect the confidentiality and integrity of communications, as well 
as authenticating each of the endpoints to each other to verify their 

Another important assumption is that telework client devices will become 
infected with malware; possible controls for this include using 
antimalware technologies, using network access control solutions that 
verify the client's security posture before granting access, and using a 
separate network at the organization's facilities for telework client 
devices brought in for internal use.

Develop a telework security policy that defines telework and remote 
access requirements.

A telework security policy should define which forms of remote access 
the organization permits, which types of telework devices are permitted 
to use each form of remote access, and the type of access each type of 
teleworker is granted. It should also cover how the organization's 
remote access servers are administered and how policies in those servers 
are updated.

As part of creating a telework security policy, an organization should 
make its own risk-based decisions about what levels of remote access 
should be permitted from which types of telework client devices. For 
example, an organization may choose to have tiered levels of remote 
access, such as allowing organization-owned personal computers (PCs) to 
access many resources, teleworker-owned PCs to access a limited set of 
resources, and other PCs and types of devices (e.g., cell phones, 
personal digital assistants [PDAs]) to access only one or two lower-risk 
resources, such as Web-based email. Having tiered levels of remote 
access allows an organization to limit the risk it incurs by permitting 
the most-controlled devices to have the most access and the 
least-controlled devices to have minimal access.

There are many factors that organizations should consider when setting 
policy regarding levels of remote access to grant; examples include the 
sensitivity of the telework, the level of confidence in the telework 
client device's security posture, the cost associated with telework 
devices, the locations from which telework is performed, and compliance 
with mandates and other policies. For telework situations that an 
organization determines are particularly high-risk, an organization may 
choose to specify additional security requirements. For example, 
high-risk telework might be permitted only from organization-issued and 
secured telework client devices that employ multifactor authentication 
and storage encryption. Organizations may also choose to reduce risk by 
prohibiting telework and remote access involving particular types of 
information, such as highly sensitive personally identifiable 
information (PII).

Ensure that remote access servers are secured effectively and are 
configured to enforce telework security policies.

Remote access servers provide a way for external hosts to gain access to 
internal resources, so their security is particularly important. In 
addition to permitting unauthorized access to resources, a compromised 
server could be used to eavesdrop on remote access communications and 
manipulate them, as well as to provide a "jumping off" point for 
attacking other hosts within the organization. It is particularly 
important for organizations to ensure that remote access servers are 
kept fully patched, and that they can only be managed from trusted hosts 
by authorized administrators. Organizations should also carefully 
consider the network placement of remote access servers; in most cases, 
a server should be placed at an organization's network perimeter so that 
it acts as a single point of entry to the network and enforces the 
telework security policy before any remote access traffic is permitted 
into the organization's internal networks.

Secure telework client devices against common threats and maintain their 
security regularly.

There are many threats to telework client devices, including malware and 
device loss or theft. Generally, telework client devices should include 
all the local security controls used in the organization's secure 
configuration baseline for its non-telework client devices.  Examples 
are applying operating system and application updates promptly, 
disabling unneeded services, and using antimalware software and a 
personal firewall. However, because telework devices are generally at 
greater risk in external environments than in enterprise environments, 
additional security controls are recommended, such as encrypting 
sensitive data stored on the devices.

Existing security controls may need to be adjusted. For example, if a 
personal firewall on a telework client device has a single policy for 
all environments, then it is likely to be too restrictive in some 
situations and not restrictive enough in others. Whenever possible, 
organizations should use personal firewalls capable of supporting 
multiple policies for their telework client devices and configure the 
firewalls properly for the enterprise environment and an external 
environment, at a minimum.

Organizations should ensure that all types of telework client devices 
are secured, including PCs, cell phones, and PDAs. For PCs, this 
includes physical security (for example, using cable locks to deter 
theft). For devices other than PCs, security capabilities and the 
appropriate security actions vary widely by device type and specific 
products, so organizations should provide guidance to device 
administrators and users who are responsible for securing telework 
consumer devices on how they should secure them.

More Information

Because telework and remote access technologies interface with so many 
other types of technologies, ranging from client devices to enterprise 
authentication services, organizations are encouraged to take advantage 
of the resources that are listed in the appendices to NIST SP 800-46 
Revision 1 for additional information.

Publications developed by NIST's Information Technology Laboratory help 
information management and information security personnel in planning 
and implementing a comprehensive approach to information security. The 
security of telework and remote access solutions depends upon attention 
to basic issues such as security planning, security awareness and 
training, risk management, application of cryptographic methods, and use 
of security controls. Organizations can draw upon NIST standards and 
guidelines on these issues and other issues related to the protection of 
networks and devices, including:

Federal Information Processing Standard (FIPS) 199, Standards for 
Security Categorization of Federal Information and Information Systems

FIPS 200, Minimum Security Requirements for Federal Information and 
Information Systems

NIST SP 800-30, Risk Management Guide for Information Technology Systems

NIST SP 800-48, Rev. 1, Guide to Securing Legacy IEEE 802.11 Wireless 

NIST SP 800-53, Rev. 2, Recommended Security Controls for Federal 
Information Systems

NIST SP 800-63 Version 1.0.2, Electronic Authentication Guidelines

NIST SP 800-64, Security Considerations in the Information System 
Development Life Cycle

NIST SP 800-70, Security Configuration Checklists Program for IT 
Products: Guidance for Checklists Users and Developers

NIST SP 800-77, Guide to IPsec VPNs

NIST SP 800-83, Guide to Malware Incident Prevention and Handling

NIST SP 800-97, Establishing Wireless Robust Security Networks: A Guide 
to IEEE 802.11i

NIST SP 800-111, Guide to Storage Encryption Technologies for End User 

NIST SP 800-113, Guide to SSL VPNs

NIST SP 800-114, User's Guide to Securing External Devices for Telework 
and Remote Access

NIST SP 800-121, Guide to Bluetooth Security

NIST SP 800-123, Guide to General Server Security

NIST SP 800-124, Guidelines on Cell Phone and PDA Security

For information about NIST standards and guidelines, as well as other 
security-related publications that help organizations protect their 
telework and remote access solutions, see NIST's Web page:



Any mention of commercial products or reference to commercial 
organizations is for information only; it does not imply recommendation 
or endorsement by NIST, nor does it imply that the products mentioned 
are necessarily the best available for the purpose.

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Received on Thu Jun 25 2009 - 00:46:46 PDT

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