Application Inspector : A Source Code Analyzer Built For Surfacing Features Of Interest

Microsoft Application Inspector is a software source code analysis tool that helps identify and surface well-known features and other interesting characteristics of source code to aid in determining what the software is or what it does. It has received attention on ZDNet, SecurityWeek, CSOOnline,, HelpNetSecurity, Twitter and more and was first featured on

Application Inspector is different from traditional static analysis tools in that it doesn’t attempt to identify “good” or “bad” patterns; it simply reports what it finds against a set of over 400 rule patterns for feature detection including features that impact security such as the use of cryptography and more. This can be extremely helpful in reducing the time needed to determine what Open Source or other components do by examining the source directly rather than trusting to limited documentation or recommendations.

The tool supports scanning various programming languages including C, C++, C#, Java, JavaScript, HTML, Python, Objective-C, Go, Ruby, PowerShell and more and includes HTML, JSON and text output formats with the default being an HTML report similar to the one shown here.

It includes a filterable confidence indicator to help minimize false positives matches as well as customizable default rules and conditional match logic.

Be sure to see our project wiki page for more help for illustrations and additional information and help.

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Application Inspector helps inform you better for choosing the best components to meet your needs with a smaller footprint of unknowns for keeping your application attack surface smaller. It helps you to avoid inclusion of components with unexpected features you don’t want.

Application Inspector can help identify feature deltas or changes between component versions which can be critical for detecting injection of backdoors.

It can be used to automate detection of features of interest to identify components that require additional scrutiny as part of your build pipeline or create a repository of metadata regarding all of your enterprise application.

Basically, we created Application Inspector to help us identify risky third party software components based on their specific features, but the tool is helpful in many non-security contexts as well.

Application Inspector v1.0 is now in GENERAL AUDIENCE release status. Your feedback is important to us. If you’re interested in contributing, please review the


We have a strong default starting base of Rules for feature detection. But there are many feature identification patterns yet to be defined and we invite you to submit ideas on what you want to see or take a crack at defining a few. This is a chance to literally impact the open source ecosystem helping provide a tool that everyone can use. See the Rules section of the wiki for more.

Getting Application Inspector

To use Application Inspector, download the relevant binary (either platform-specific or the multi-platform .NET Core release). If you use the .NET Core version, you will need to have .NET Core 3.0 or later installed. See the or files for help.

It might be valuable to consult the project wiki for additional background on Rules, Tags and more used to identify features. Tags are used as a systematic heirarchal nomenclature e.g. Cryptography.Protocol.TLS to more easily represent features.


Application Inspector is a command-line tool. Run it from a command line in Windows, Linux, or MacOS.

dotnet AppInspector.dll or on Windows simply AppInspector.exe

Microsoft Application Inspector 1.0.25
ApplicationInspector 1.0.25

Microsoft Corporation. All rights reserved

No verb selected.

-analyze Inspect source directory/file/compressed file (.tgz|zip) against defined characteristics
-tagdiff Compares unique tag values between two source paths
-tagtest Test presence of smaller set or custom tags in source (compare or verify modes)
-exporttags Export default unique rule tags to view what features may be detected
-verifyrules Verify rules syntax is valid
-help Display more information on a specific command
-version Display version information


Command Help

Usage: dotnet AppInspector.dll [arguments] [options]

dotnet AppInspector.dll -description of available commands
dotnet AppInspector.dll -options description for a given command

Analyze Command

Usage: dotnet AppInspector.dll analyze [arguments] [options]


-s, –source-path Required. Path to source code to inspect (required)
-o, –output-file-path Path to output file. Ignored with -f html option which auto creates output.html
-f, –output-file-format Output format [html|json|text]. Default = html
-e, –text-format Match text format specifiers
-r, –custom-rules-path Custom rules path
-t, –tag-output-only Output only contains identified tags. Default = false
-i, –ignore-default-rules Ignore default rules bundled with application. Default = false
-d, –allow-dup-tags Output only non-unique tag matches. Default = false
-c, –confidence-filters Output only matches with confidence [high|medium|low]. Default = high,medium
-k, –file-path-exclusions Exclude source files [none|]. Default = sample,example,test,docs,.vs,.git
-x, –console-verbosity Console verbosity [high|medium|low|none]. Default = medium
-l, –log-file-path Log file path. Default is /log.txt
-v, –log-file-level Log file level [Debug|Info|Warn|Error|Fatal|Off]. Default = Error

Scan a project directory, with output sent to “output.html” (default behavior includes launching default browser to this file)

dotnet AppInspector.dll analyze -s /home/user/myproject

Add custom rules (can be specified multiple times)

dotnet AppInspector.dll analyze -s /home/user/myproject -r /my/rules/directory -r /my/other/rules

Write to JSON format

dotnet AppInspector.dll analyze -s /home/user/myproject -f json

Tagdiff Command

Use to analyze and report on differences in tags (features) between two project or project versions e.g. v1, v2 to see what changed

Usage: dotnet AppInspector.dll tagdiff [arguments] [options]


–src1 Required. Source 1 to compare (required)
–src2 Required. Source 2 to compare (required
-t, –test-type Type of test to run [equality|inequality]. Default = equality
-r, –custom-rules-path Custom rules path
-i, –ignore-default-rules Ignore default rules bundled with application. Default = false
-o, –output-file-path Path to output file
-x, –console-verbosity Console verbosity [high|medium|low]. Default = medium
-l, –log-file-path Log file path
-v, –log-file-level Log file level [error|trace|debug|info]. Default = error

Simplist way to see the delta in tag features between two projects

dotnet AppInspector.dll tagdiff –src1 /home/user/project1 –src2 /home/user/project2

Basic use

dotnet AppInspector.dll tagdiff –src1 /home/user/project1 –src2 /home/user/project2 -t equality

Basic use

dotnet AppInspector.dll tagdiff –src1 /home/user/project1 –src2 /home/user/project2 -t inequality

TagTest Command

Used to verify (pass/fail) that a specified set of rule tags is present or not present in a project e.g. user only wants to know true/false if crytography is present as expected or if personal data is not present as expected and get a simple yes/no result rather than a full analyis report.

Note: The user is expected to use the custom-rules-path option rather than the default ruleset because it is unlikely that any source package would contain all of the default rules. Instead, create a custom path and rule set as needed or specify a path using the custom-rules-path to point only to the rule(s) needed from the default set.
Otherwise, testing for all default rules present in source will likely yield a false or fail result in most cases.

Usage: dotnet AppInspector.dll tagtest [arguments] [options

-s, –source-path Required. Source to test (required)
-t, –test-type Test to perform [rulespresent|rulesnotpresent]. Default = rulespresent
-r, –custom-rules-path Custom rules path
-i, –ignore-default-rules Ignore default rules bundled with application. Default = true
-o, –output-file-path Path to output file
-x, –console-verbosity Console verbosity [high|medium|low]. Default = medium
-l, –log-file-path Log file path
-v, –log-file-level Log file level

Simplest use to see if a set of rules are all present in a project

dotnet AppInspector.dll tagtest -s /home/user/project1 -r /home/user/myrules.json

Basic use

dotnet AppInspector.dll tagtest -s /home/user/project1 -r /home/user/myrules.json -t rulespresent

Basic use

dotnet AppInspector.dll tagtest -s /home/user/project1 -r /home/user/myrules.json -t rulesnotpresent

ExportTags Command

Simple export of the ruleset schema for tags representing what features are supported for detection

Usage: dotnet AppInspector.dll exporttags [arguments] [options]

-r, –custom-rules-path Custom rules path
-i, –ignore-default-rules Ignore default rules bundled with application. Default = false
-o, –output-file-path Path to output file
-x, –console-verbosity Console verbosity [high|medium|low]. Default = medium

Export default rule tags to console

dotnet AppInspector.dll exporttags

Using output file

dotnet AppInspector.dll exporttags -o /home/user/myproject/exportags.txt

With custom rules and output file

dotnet AppInspector.dll exporttags -r /home/user/myproject/customrules -o /hom/user/myproject/exportags.txt

Verify Command

Verification that ruleset is compatible and error free for import and analysis

Usage: dotnet AppInspector.dll verifyrules [arguments]


-r, –custom-rules-path Custom rules path
-i, –ignore-default-rules Ignore default rules bundled with application. Default = false
-o, –output-file-path Path to output file
-x, –console-verbosity Console verbosity [high|medium|low]. Default = medium.

Simplist case to verify default rules

dotnet AppInspector.dll verifyrules

Using custom rules only

dotnet AppInspector.dll verifyrules -r /home/user/myproject/customrules -i

Build Instructions

Building from source requires .NET Core 3.0. Standard dotnet build commands can be run from the root source folder.

Framework Dependent

dotnet build -c Release

Platform Targeted Portable

dotnet publish -c Release -r win-x86
dotnet publish -c Release -r linux-x64
dotnet publish -c Release -r osx-x64