DISCUSSION [NIST SP 800-171 R2]
Mobile code technologies include Java, JavaScript, ActiveX, Postscript, PDF, Flash animations, and VBScript. Decisions regarding the use of mobile code in organizational systems are based on the potential for the code to cause damage to the systems if used maliciously. Usage restrictions and implementation guidance apply to the selection and use of mobile code installed on servers and mobile code downloaded and executed on individual workstations, notebook computers, and devices (e.g., smart phones). Mobile code policy and procedures address controlling or preventing the development, acquisition, or introduction of unacceptable mobile code in systems, including requiring mobile code to be digitally signed by a trusted source.
FURTHER DISCUSSION
Ensure mobile code is authorized to execute in company systems only in accordance with policy and technical configuration, and that unauthorized mobile code is not. Monitor the use of mobile code through boundary devices (e.g., firewalls), audit logs, or security utilities (e.g., mobile device management, advanced endpoint protection) and implement remediation activities as needed.
The first intent of this practice is to ensure the limits of mobile code usage and usage restrictions are documented and enforced. This includes documenting all authorizations for the use of mobile code and ensuring it is not used in other ways. Usage restrictions and implementation guidance apply to the selection and use of mobile code installed on servers and mobile code downloaded and executed on individual workstations and devices to include all mobile devices and smart phones.
The second intent is to monitor the use of mobile code and implement remediation steps if its use does not align with policy.
Example
Your company has decided to prohibit the use of Flash, ActiveX, and Java plug-ins for web browsers on all of its computers [a]. To enforce this policy you configure the computer baseline configuration to disable and deny the execution of mobile code [a]. You implement an exception process to re-enable mobile code execution only for those users with a legitimate business need [a].
One department complains that a web application they need to perform their job no longer works. You meet with them and verify that the web application uses ActiveX in the browser. You submit a change request with the Change Review Board. Once the change is approved, you reconfigure the department’s computers to allow the running of ActiveX in the browser. You also configure the company firewall to alert you if ActiveX is used by any website but the allowed one [b]. You set a reminder for yourself to check in with the department at the end of the year to verify they still need that web application.
Potential Considerations
Are there defined limits of mobile code usage and established usage restrictions, which specifically authorize use of mobile code (e.g., Java, JavaScript, ActiveX, PDF, Flash, Shockwave, Postscript, VBScript) within the information system [a]? 74
Is the use of mobile code documented, monitored, and managed (e.g., Java, JavaScript, ActiveX, PDF, Flash, Shockwave, Postscript, VBScript) [b]?75
Copyright
Copyright 2020, 2021 Carnegie Mellon University and The Johns Hopkins University Applied Physics Laboratory LLC.
Copyright 2021 Futures, Inc.
This material is based upon work funded and supported by the Department of Defense under Contract No. FA8702-15-D-0002 with Carnegie Mellon University for the operation of the Software Engineering Institute, a federally funded research and development center, and under Contract No. HQ0034-13-D-0003 and Contract No. N00024-13-D-6400 with the Johns Hopkins University Applied Physics Laboratory LLC, a University Affiliated Research Center.
The view, opinions, and/or findings contained in this material are those of the author(s) and should not be construed as an official Government position, policy, or decision, unless designated by other documentation.
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