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Implementing Application Whitelisting

First published 2012; Latest version April 2019

Introduction

Application whitelisting is one of the most effective mitigation strategies in ensuring the security of systems. As such, application whitelisting forms part of the Essential Eight from the Strategies to Mitigate Cyber Security Incidents.

This document provides guidance on what application whitelisting is, what application whitelisting is not, and how to implement application whitelisting.

What application whitelisting is

Application whitelisting is a security approach designed to protect against malicious code (also known as malware) executing on systems. When implemented properly it ensures that only authorised applications (e.g. executables, software libraries, scripts and installers) can be executed.

While application whitelisting is primarily designed to prevent the execution and spread of malicious code, it can also prevent the installation or use of unauthorised applications.

What application whitelisting is not

The following approaches are not considered to be application whitelisting:

  • providing a portal or other means of installation for authorised applications
  • using web or email content filters to prevent users from downloading applications from the Internet
  • checking the reputation of an application using a cloud-based service before it is executed
  • using a next-generation firewall to identify whether network traffic is generated by an approved application.

How to implement application whitelisting

Implementing application whitelisting involves the following high-level steps:

  • identifying applications that are authorised to execute
  • developing application whitelisting rules to ensure only those authorised applications can execute
  • maintaining the application whitelisting rules using a change management program.

When determining how to enforce application whitelisting, the following methods are considered suitable if implemented correctly:

  • cryptographic hash rules
  • publisher certificate rules (combining both publisher names and product names)
  • path rules (ensuring file system permissions are configured to prevent unauthorised modification of folder and file permissions, folder contents and individual files).

Conversely, the use of file names, package names or any other easily changed application attribute is not considered suitable as a method of application whitelisting.

To ensure application whitelisting has been appropriately implemented, testing should be undertaken on a regular basis to check for misconfigurations of file system permissions and other ways of bypassing application whitelisting rules or executing unauthorised applications.

In addition to preventing the execution of unauthorised applications, application whitelisting can contribute to the identification of attempts by an adversary to execute malicious code. This can be achieved by configuring application whitelisting to generate event logs for failed execution attempts. Such event logs should ideally include information such as the name of the blocked file, the date/time stamp and the username of the user attempting to execute the file.

Finally, it is important that application whitelisting does not replace antivirus and other security software already in place on systems. Using multiple security solutions together can contribute to an effective defence-in-depth approach to preventing the compromise of systems.

Further information

The Australian Government Information Security Manual (ISM) assists in the protection of information that is processed, stored or communicated by organisations’ systems. It can be found at https://www.cyber.gov.au/ism.

The Strategies to Mitigate Cyber Security Incidents complements the advice in the ISM. The complete list of strategies can be found at https://www.cyber.gov.au/publications/strategies-to-mitigate-cyber-security-incidents.

Contact details

Organisations or individuals with questions regarding this advice can email asd.assist@defence.gov.au or call 1300 CYBER1 (1300 292 371).

Date
April 30th, 2019