OWASP Appsensor

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![Appsensor-header.jpg](Appsensor-header.jpg "Appsensor-header.jpg")
![_flagship_big.jpg](_flagship_big.jpg "_flagship_big.jpg")

The AppSensor project defines a conceptual framework and methodology that offers prescriptive guidance to implement intrusion detection and automated response into applications.

The project offers a comprehensive guide and a reference implementation. These resources can be used by architects, developers, security analyst and system administrators to plan, implement and monitor an AppSensor system.


If you walk into a bank and try opening random doors, you will be identified, led out of the building and possibly arrested. However, if you log into an online banking application and start looking for vulnerabilities no one will say anything. This needs to change! As critical applications continue to become more accessible and inter-connected, it is paramount that critical information is sufficiently protected. We must also realize that our defenses may not be perfect. Given enough time, attackers can identify security flaws in the design or implementation of an application.

In addition to implementing layers of defense within an application, we must identify malicious individuals before they are able to identify any gaps in our defenses. The best place to identify malicious activity against the application is within the application itself. Network based intrusion detection systems are not appropriate to handle the custom and intricate workings of an enterprise application and are ill-suited to detect attacks focusing on application logic such as authentication, access control, etc. This project delivers a framework which can be used to build a robust system of attack detection, analysis, and response within an enterprise application.

Detect and Respond to Attacks from Within the Application


AppSensor defines over 50 different detection points which can be used to identify a malicious attacker.


AppSensor provides guidance on how to respond once a malicious attacker has been identified. Possible actions include: logging out the user, locking the account or notifying an administrator. More than a dozen response actions are described.

Defending the Application

An attacker often requires numerous probes and attack attempts in order to locate an exploitable vulnerability within the application. By using AppSensor it is possible to identify and eliminate the threat of an attacker before they are able to successfully identify an exploitable flaw.


  • CrossTalk, The Journal of Defense Software Engineering
    • Creating Attack-Aware Software Applications with Real Time Defenses, Vol. 24, No. 5, Sep/Oct 2011


OWASP AppSensor is free to use.


The guide is licensed under the Creative Commons Attribution-ShareAlike 3.0 license, so you can copy, distribute and transmit the work, and you can adapt it, and use it commercially, but all provided that you attribute the work and if you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one.

Reference Implementation

The reference implementation is licensed under the MIT License, which is a permissive (commercial-friendly) license only requiring you to include a copy of the license upon distribution or copying.

© OWASP Foundation


News and Events

Code Repository

In Print


The AppSensor Guide and CISO Briefing can be purchased at cost as print on demand books.


What is AppSensor?

Detect and respond to attacks from within the application. This project includes both a well documented idea (the Guide) and a reference implementation (the Code).

Detect and respond to attacks from within the application. This project includes both a well documented idea (the Guide) and a reference implementation (the Code).

Intro for Developers

Intro for Developers


Two-sided US Letter or A4

Two-sided US Letter or A4

AppSensor Website

AppSensor Website


See the AppSensor website for an introduction and quick start instructions.

See the AppSensor website for an introduction and quick start instructions.




12-page US Letter booklet

12-page US Letter booklet

Project Founder

Project Founder

Project Leaders

Project Leaders

    • <a href=":Category:OWASP_ModSecurity_Core_Rule_Set_Project" title=>OWASP ModSecurity Core Rule Set</a>
    • <a href=":Category:OWASP_ModSecurity_Core_Rule_Set_Project" title=>OWASP ModSecurity Core Rule Set</a>



All OWASP projects rely on the voluntary efforts of people in the software development and information security sectors. They have contributed their time and energy to make suggestions, provide feedback, write, review and edit documentation, give encouragement, make introductions, produce demonstration code, promote the concept, and provide OWASP support. They participated via the project’s mailing lists, by developing code, by updating the wiki, by undertaking research studies, and through contributions during the AppSensor working session at the OWASP Summit 2011 in Portugal and the AppSensor Summit at AppSec USA 2011. Without all their efforts, the project would not have progressed to this point, and this guide would not have been completed.

  • Josh Amishav-Zlatin
  • Ryan Barnett
  • Simon Bennetts
  • Joe Bernik
  • Rex Booth
  • Luke Briner
  • Rauf Butt
  • Juan C Calderon
  • Fabio Cerullo
  • Marc Chisinevski
  • Robert Chojnacki
  • Michael Coates
  • Dinis Cruz
  • Sumanth Damaria
  • August Detlefsen
  • Ryan Dewhurst
  • Sean Fay
  • Timo Goosen
  • Dennis Groves
  • Randy Janida
  • Chetan Karande
  • Eoin Keary
  • Alex Lauerman
  • Junior Lazuardi
  • Benjamin-Hugo LeBlanc
  • Jason Li
  • Manuel López Arredondo
  • Bob Maier
  • Jim Manico
  • Sherif Mansour Farag
  • John Melton
  • Mark Miller
  • Rich Mogull
  • Craig Munson
  • Louis Nadeau
  • Giri Nambari
  • Erlend Oftedal
  • Jay Reynolds
  • Chris Schmidt
  • Sahil Shah
  • Eric Sheridan
  • John Steven
  • Raphael Taban
  • Alex Thissen
  • Don Thomas
  • Christopher Tidball
  • Stephen de Vries
  • Kevin W Wall
  • Colin Watson
  • Mehmet Yilmaz

OWASP Summer of Code 2008

The AppSensor Project was initially supported by the OWASP Summer of Code 2008, leading to the publication of the book AppSensor v1.1.

Google Summer of Code 2012

Additional development work on SOAP web services was kindly supported by the Google Summer of Code 2012.

OWASP Code Sprint 2015

Development work was also supported by the OWASP Summer Code Sprint 2015.

Other Acknowledgements

The project has also benefitted greatly from the generous contribution of time and effort by many volunteers in the OWASP community including those listed above, and contributors to the OWASP ESAPI project, members of the former OWASP Global Projects Committee, the OWASP Board, OWASP staff and support from the OWASP Project Reboot initiative. The v2 code and documentation were conceived during the AppSensor Summit held during AppSec USA 2011 in Minneapolis.

Road Map and Getting Involved

Please join the project’s mailing lists to keep up-to-date with what’s going on, and to contribute your ideas, feedback, and experience:

Current activities

Non code

v2 Code

The current code being worked on is located on GitHub

The code has been fully rewritten. v2.0.0 final was released in late January 2015. v2.1.0 final was released in June 2015. v2.2.0 final was released in September 2015

The main reason for the rewrite was to allow a client-server style model as opposed to requiring AppSensor be fully embedded in the application. You can now have a central server collecting events from multiple applications and performing analysis. These front-end applications can be in any language as long as they speak rest/soap. There’s been a host of other changes, but this was the primary one. A number of starter ideas for coding, user interface and documentation have been outlined via the mailing list at 17th March 2014.

if you want to work on ANYTHING, please let jtmelton[@]gmail.com know.

Code Roadmap

Q4 2015 (2.0)

  • Jan - v 2.0.0 final release -> DONE

Q4 2014 (2.0)

  • Oct - v 2.0.0 release candidate -> DONE
  • Jan 2015 (delay due to bug) - v 2.0.0 final -> DONE
  • Additional unit tests -> DONE
  • Move appsensor.org site over from static html to python -> NOT NECESSARY
  • Finish up user documentation at appsensor.org -> DONE

June 2015 (2.1)

  • Add at least 1 attack emitter for DEVOPS visualization (JMX -> SNMP, syslog, SNMP, .. something) (github issue) -> DONE
  • Sample application / demo (github issue) -> DONE
  • Finish up developer documentation on github and appsensor.org (github issue) -> DONE
  • Preparation for GSOC 2015 submission -> DONE - see GSoC2015_Ideas - Update - OWASP not selected

September 2015 (2.2)

  • First version of administration UI for appsensor (monitoring UI) (github issues here and here) -> DONE

January 2016 (2.3)

  • Get CI server (cloudbees?) setup (github issue) -> DONE
  • Video demo of setting up appsensor (screen capture) (related to sample apps)
  • New detection point implementations (github issue)
  • AOP examples of detection point implementations

May 2016 (2.4)

  • Trend monitoring implementation (github issue)
  • Additional integrations for reporting (graphite, ganglia -> see list supported by codahale metrics)

Past activities

September 2015 Final release v2.2.0 code

June 2015 Final release v2.1.0 code

April 2015 CISO Briefing booklet published

February 2015 Introduction for Developers flyer published

January 2015 Final release v2.0.0 code

May 2014 Finalisation and publication of the AppSensor Guide v2.0

November, 2013 - AppSensor 2.0 hackathon, and document writing & review at AppSecUSA 2013, New York

2012-2013 - Active Development of next AppSensor book

September, 2011 - AppSensor Summit at AppSec USA 2011, Minneapolis

September, 2010 - Presented at AppSecUSA slides

June, 2010 - Active ESAPI Integration Underway

November, 2009 OWASP DC, November 2009

2009 v1.2 in the works, demo application in development

May, 2009 - AppSec EU Poland - Presentation (PPT) (Video)

January, 2009 - v1.1 Released - Beta Status

November, 2008 - AppSensor Talk at OWASP Portugal

November, 2008 - v1.0 Released - Beta Status

April 16, 2008 - Project Begins

Detection Points

Below are the primary detection points defined within AppSensor. These are just the titles; the document contains descriptions, examples and considerations for implementing these detection points.

'''Detailed Detection Point Information Here '''

Response Action Information Here

Summary of Information Detection Categories:

RE - Request

AE - Authentication

SE - Session

ACE - Access Control

IE - Input

EE - Encoding

CIE - Command Injection

FIO - File IO

HT - Honey Trap

UT - User Trend

STE - System Trend

RP - Reputation

Signature Based Event Titles

ID Event

RE1 Unexpected HTTP Command

RE2 Attempt to Invoke Unsupported HTTP Method

RE3 GET When Expecting POST

RE4 POST When Expecting GET

RE5 Additional/Duplicated Data in Request

RE6 Data Missing from Request

RE7 Unexpected Quantity of Characters in Parameter

RE8 Unexpected Type of Characters in Parameter

AE1 Use Of Multiple Usernames

AE2 Multiple Failed Passwords

AE3 High Rate of Login Attempts

AE4 Unexpected Quantity of Characters in Username

AE5 Unexpected Quantity of Characters in Password

AE6 Unexpected Type of Character in Username

AE7 Unexpected Type of Character in Password

AE8 Providing Only the Username

AE9 Providing Only the Password

AE10 Adding POST Variable

AE11 Missing POST Variable

AE12 Utilization of Common Usernames

SE1 Modifying Existing Cookie

SE2 Adding New Cookie

SE3 Deleting Existing Cookie

SE4 Substituting Another User’s Valid Session ID or Cookie

SE5 Source IP Address Changes During Session

SE6 Change Of User Agent Mid Session

ACE1 Modifying URL Argument Within a GET for Direct Object Access Attempt

ACE2 Modifying Parameter Within a POST for Direct Object Access Attempt

ACE3 Force Browsing Attempt

ACE4 Evading Presentation Access Control Through Custom POST

IE1 Cross Site Scripting Attempt

IE2 Violation of Implemented White Lists

IE3 Violation Of Implemented Black Lists

IE4 Violation of Input Data Integrity

IE5 Violation of Stored Business Data Integrity

IE6 Violation of Security Log Integrity

EE1 Double Encoded Character

EE2 Unexpected Encoding Used

CIE1 Blacklist Inspection for Common SQL Injection Values

CIE2 Detect Abnormal Quantity of Returned Records

CIE3 Null Byte Character in File Request

CIE4 Carriage Return or Line Feed Character In File Request

FIO1 Detect Large Individual File

FIO2 Detect Large Number of File Uploads

HT1 Alteration to Honey Trap Data

HT2 Honey Trap Resource Requested

HT3 Honey Trap Data Used

Behavior Based Event Titles UT1 Irregular Use of Application

UT2 Speed of Application Use

UT3 Frequency of Site Use

UT4 Frequency of Feature Use

STE1 High Number of Logouts Across The Site

STE2 High Number of Logins Across The Site

STE3 Significant Change in Usage of Same Transaction Across The Site

RP1 Suspicious or Disallowed User IP Address

RP2 Suspicious External User Behavior

RP3 Suspicious Client-Side Behavior

RP4 Change to Environment Threat Level


Introductory Briefings

Developers   Architects   CISOs
Appsensor-developer-small.jpg   Appsensor_crosstalk_small.jpg   Appsensor-cisobriefing-small.jpg

The CISO briefing is also available to buy at cost in print.

AppSensor Website




AppSensor Guide


Automated Application Defenses to Thwart Advanced Attackers (Slides & Audio)

July, 2010 - OWASP London (UK) - Real Time Application Attack Detection and Response with OWASP AppSensor

June, 2010 - OWASP Leeds/North (UK) - OWASP AppSensor - The Self-Aware Web Application

June, 2010 - Video presentation - Automated Application Defenses to Thwart Advanced Attackers

November, 2009 - AppSec DC - Defend Yourself: Integrating Real Time Defenses into Online Applications

May, 2009 - OWASP Podcast #51

May, 2009 - AppSec EU Poland - Real Time Defenses against Application Worms and Malicious Attackers

November, 2008 - OWASP Summit Portugal 2008 PPT

Video Demos of AppSensor

Detecting Multiple Attacks & Logging Out Attacker

Detecting XSS Probes

Detecting URL Tampering

Detecting Verb Tampering

Source Documents / Artwork

Project About



AppSensor Project Category:OWASP Project Category:OWASP_Builders Category:OWASP_Defenders Category:OWASP_Document Category:OWASP_Download Category:SAMM-EH-3 Category:SAMM-SA-2 Category:SAMM-VM-3


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