Application Whitelisting: What it is and why it’s good

Application whitelisting 1Application Whitelisting (AWL) is a technology created to keep computer systems safe from unwanted software, including malware.  It works together with Application Blacklisting to keep malware and other unauthorized software from running on a system.

What Is the Advantage of Application Whitelisting?

AWL controls the software that is allowed to run on a computer system. It does this by denying access to any application that has not been specifically whitelisted, i.e. deemed safe and allowed by the administrator.

Application blacklisting is another way to control the software allowed on a system. It denies access to any application that has been blacklisted, i.e. deemed malicious or unwanted.

From a security perspective, AWL is considered more secure. This is because it allows a set of trusted applications and blocks everything else. In theory, this would even stop dreaded “zero day” attacks.

Zero-day attacks are attacks that exploit a software vulnerability that was previously unknown or undisclosed by the software vendor. The first day one is observed is known as “day zero”.

Traditional blacklists cannot stop malware that uses a zero-day attack. This is because the attack has never been observed and therefore cannot be blacklisted.

However, application whitelisting can stop such an attack. All applications not whitelisted are blocked.

What Are the Disadvantages of Application Whitelisting?

Whitelisting can be a safe approach to controlling the applications on a computer system – but it can also be onerous to manage.

The number of legitimate software applications stretches into the millions. While users may wish to install a safe application for legitimate reasons, they would be denied from doing so if the application was not on the system’s whitelist.

This can create inefficiency and frustration in the workplace, where dozens or even hundreds of users with a broad range of needs require many different applications to perform their roles.

Application whitelisting 2How Does Whitelisting Work?

AWL requires the total contents of a file to be read one time.  This reading is used to create a hashed, aka digital signature of the file’s contents.  The signatures are indexed by file name.  When a new application enters the system, its signature is compared to the signature stored in the whitelist database.  If the filename and the signature do not match, the application is denied.

Conversely, when an antivirus blacklist checks a file to see if it is legitimate, it must compare the file contents against the database of signatures of every previously identified malware variant.  That activity takes up much of the CPU cycle on computers running antivirus software.  Computers work harder to blacklist than they do to whitelist.

Where Should AWL be Used?

  1. On centrally managed hosts connected to other computers
  2. By hosts in a high-risk environment
  3. On laptops or kiosks where users do not have administrative privileges

Why Doesn’t Everyone Use Application Whitelisting?

While AWL does a great job of protecting against malicious applications, it also can prevent access of legitimate applications.  This can make a system difficult to use.  Many IT admins only use blacklisting instead of what they see as the over-the-top security of whitelisting.  There have been instances when AWL blocks non-malicious code, which then can cause a system to malfunction.

Many operating systems have “deny by default” systems.  However, in order to manage these systems the IT administrator has to identify the individual files that should, and should not be allowed.  Modern AWL systems are able to track when approved changes are made and manage the whitelist accordingly.

Another complaint about AWL is that it slows down the work of an end-user who needs to add a program to a system.  However, modern AWL solutions can be configured so that trusted end users are enabled to make controlled changes to their systems. Another way to manage AWL is for an IT admin to pre-approve applications that are allowed to be installed, so when the end user attempts to install the application it proceeds without a problem.

Developers traditionally had a problem with AWL because it is their job to develop executable code, which is exactly what AWL solutions seek to block.  However, the AWL solution can be programmed to “trust” development tools as they are used to create a new code.  Once the AWL solution trusts a tool, all of the code developed with that tool will be automatically added to the whitelist.

An AWL solution should be built to work together with your system management and software deployment.  If you manage your endpoints with Remote Management and Monitoring tools, then the AWL Solution should be programmed to “trust” the endpoint agents.
Application whitelisting 3

Implementation of AWL

  1. Identify what needs to be monitored by whitelisting, including the operating system, applications, and the interfaces of other integrated systems
  2. Determine whether to block execution of unauthorized applications or to just monitor them
  3. Determine which systems have built in whitelisting, and which require a purchased product
  4. If purchasing a product, determine the most effective cryptography and solution architecture
  5. Prior to installing AWL scan the system for malware.
  6. Test the AWL technology in monitoring mode to ensure that it allows security updates to run
  7. Test the AWL technology by executing a whitelist application, and blocking the execution of a blacklist application
  8. Dedicate personnel to monitor the system

Whitelisting Software - Paid

  1. Airlock Digital was founded by two Australian information security experts to address whitelisting challenges.
  2. Lumension offers an “audit only logging mode” for easy deployment
  3. Carbon Black, formerly Bit9, bills itself as a “Next-Gen endpoint security leader”
  4. McAfee Application Control has an inventory feature to manage application related files.
  5. Digital Guardian bolstered its whitelisting capability when it acquired Savant in 2015

An integrated single AWL solution is the best bet for an organization that does not have adequate staff to develop, test and deploy AWL policies.

Whitelisting Software - Free

  1. Applocker is included with Microsoft 7, 8, and 10
  2. Gatekeeper is Apple’s whitelisting solution
  3. SELinex is Linux’s whitelisting application control
  4. Logstash is an opensource version of Splunk

Application whitelisting 4Management of AWL

Once the system is up and running, a designated IT admin should be responsible for keeping it up to date.  Tasks should include updating the whitelist with new applications, applying any issued patches to the program, deploying the whitelisting to additional platforms, and performing periodic tests to ensure the software is working as promised.

Other Uses of Whitelisting Technology

In addition to only permitting accepted applications to run on a system, AWL has the following attributes:

  1. It can stop changes to files, or monitor and report changes to files, providing a level of file integrity
  2. It keeps an inventory of applications and application versions installed on hosts
  3. It captures characteristics of files, such as cryptographic file hashes, which can be used to respond to a malicious incident

The U.S. National Institute of Standards and Technology provides a Guide to whitelisting application technology.  Recommendations include using the whitelisting mechanisms that are built into operating systems, and using mechanisms that identify applications by digital signatures, as well as path and file name.

There are many tools in the cybersecurity toolbox.  Application Whitelisting can provide an added modicum of security.  In the case of a high risk host, or a managed environment with central control, application whitelisting can provide a more secure system than a simple antivirus blacklisting program.

Related Resources

Calyptix AccessEnforcer

Deploying Application Whitelisting

Homeland Security AWL Strategic Planning Guide

NIST Guide to Application Whitelisting

The Ransomware Plague in Hospitals and Healthcare

Ten Common Misconceptions to Application Whitelisting

Written by Calyptix

 - April 17, 2017

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