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Revision as of 10:03, 22 February 2013

About This Document

These detection points are part of the OWASP AppSensor project which advocates bringing intelligent intrusion detection inside the application. These detection points can be used to identify a malicious user that is probing for vulnerabilities or weaknesses within your application.

Read more about why application logging is the way to go.

Contents


Detection Points

RequestException

RE1: Unexpected HTTP Command

ID

RE1

Title

Unexpected HTTP Command

Category

RequestException

Description

An HTTP request is received which contains unexpected/disallowed commands.

Considerations

A list of accepted commands should be generated (i.e. GET and POST) and all other HTTP commands should generate an event. See HTTP/1.1: Method Definitions.

Tuning

Browsers and proxies using the HEAD method to check whether the content of a file has changed.

Examples

Instead of a GET or POST request, the user sends a TRACE request to the application.

Cross references:

Code

[Java] [.Net] [PHP]

RE2: Attempt to Invoke Unsupported HTTP Method

ID

RE2

Title

Attempt to Invoke Unsupported HTTP Method

Category

RequestException

Description

An HTTP request is received which contains a non-existent HTTP command (does not match anything in this list: HEAD, GET, POST, PUT, DELETE, TRACE, OPTIONS, CONNECT).

Considerations

-

Tuning

-

Examples

Instead of a GET or POST request, the user sends a TEST request to the application (TEST is not a valid HTTP request method).

Code

[Java] [.Net] [PHP]

RE3: GET When Expecting POST

ID

RE3

Title

GET When Expecting POST

Category

RequestException

Description

A page which is expecting only POST requests, is requested by HTTP method GET.

Considerations

Some pages may be designed to receive both GET and POST requests.

Tuning

Some resources may allow both GET and POST methods e.g. an edit form may be hyperlinked using a parameter value defining the record to be edited, but the form is submitted by POST to itself. Users may bookmark a page that is the result of a POST and return to it at a later date.

Examples

The user sends a GET request to a page which has only been used for POSTs.

Code

[Java] [.Net] [PHP]

RE4: POST When Expecting GET

ID

RE4

Title

POST When Expecting GET

Category

RequestException

Description

A page which is expecting only GET requests, receives a POST.

Considerations

-

Tuning

(same as RE3)

Examples

The user utilizes a proxy tool to build a custom POST request and sends it to a page which has been accessed by GET requests.

Code

[Java] [.Net] [PHP]

RE5: Additional/Duplicated Data in Request

ID

RE5

Title

Additional/Duplicated Data in Request

Category

RequestException

Description

Additional unexpected parameters or HTTP headers, or duplicates, are received with the request.

Considerations

Additional parameters may be an attempt to override values or to exploit unexposed functionality. Duplicated parameters may be an indication of attempted HTTP parameter pollution.

Beware of firing this detector when additional cookies, not used by the application, are found (as opposed to duplicated cookies) since these may relate to third-party code (e.g. advertisements, analytics) or some other application.

Note that extra HTTP headers may be added by intermediate proxies, and unless the network configuration is fixed (an internal network perhaps), additional headers cannot be controlled and thus cannot be used to infer existence of a potential attacker.

Tuning

Links from third party sites/services may included additional parameters (e.g. from search engines, from advertisements). Additional cookies headers may be added by other applications or by third parties such as advertisers, and there may be very little control over these. Additional HTTP headers may be added by intermediate network devices (e.g. for traffic management).

Examples

Example 1: Additional form or URL parameters submitted with request (e.g. debug=1, servervariable=2000).

Example 2: A parameter is defined more than once in the URL Query String.

Example 3: An HTTP header is duplicated.

Example 4: An additional HTTP header is found.

Example 5: A URL path parameter with the same name as a form parameter is sent with the request

Code

[Java] [.Net] [PHP]

RE6: Data Missing from Request

ID

RE6

Title

Data Missing from Request

Category

RequestException

Description

Expected parameters or HTTP headers are missing from the request.

Considerations

Bookmarking and use of a browser's "back button" can lead to requests without the expected parameters.

Tuning

A bookmarked page may be missing the required POST parameters (see also RE3). Users may choose to send a blank or different User Agent header value.

Examples

Example 1: A page is requested without any of the required form parameters.

Example 2: The HTTP-Accept header is not present in a request.

Code

[Java] [.Net] [PHP]

RE7: Unexpected Quantity of Characters in Parameter

ID

RE7

Title

Unexpected Quantity of Characters in Parameter

Category

RequestException

Description

The user provides a parameter value with a large number of characters.

Considerations

-

Tuning

If the input field does not have client-side validation and/or MAXLENGTH attributes, a user might inadvertently copy in some text that is longer than expected.

Examples

Example 1: The user submits a form field with more characters than the form's maxlength attribute and client-side validation would allow

Example 2: The user submits data in a form's hidden field which is longer than expected.

Code

[Java] [.Net] [PHP]

RE8: Unexpected Type of Characters in Parameter

ID

RE8

Title

Unexpected Type of Characters in Parameter

Category

RequestException

Description

The user provides a parameter value containing characters outwith the expected range.

Considerations

-

Tuning

Text fields may include text from copy and paste operations that contain illegal characters.

Examples

Example 1: The user sends an HTTP header containing a line break character.

Example 2: The user sends a URL parameter value that contains ASCII characters below 20 or above 7E.

Code

[Java] [.Net] [PHP]

AuthenticationException

AE1: Use of Multiple Usernames

ID

AE1

Title

Use of Multiple Usernames

Category

AuthenticationException

Description

Multiple usernames are attempted when logging into the application.

Considerations

The assignment of login attempts to a user can be based on a sessionID given to the user when they first visit the website. Correlating based on IP address is difficult since multiple users could be using the site from the same IP address (e.g. corporate NAT).

Tuning

-

Examples

User first tries username 'bob', then username 'sue', then 'steve', etc.

Code

[Java] [.Net] [PHP]

AE2: Multiple Failed Passwords

ID

AE2

Title

Multiple Failed Passwords

Category

AuthenticationException

Description

For a single username, multiple bad passwords, or other authentication credentials, are entered.

Considerations

See Popularity is Everything section 4 - Attack-Detection Scenarios for ideas about tracking use of unsuccessful passwords and looking whether these are used against multiple accounts.

Tuning

A users providing the same wrong password more than once may be different to different wrong passwords. See Account Lockout, Bill Cheswick, Episode 76, OWASP Podcast, September 22, 2010.

Examples

Example 1: User tries username:password combination of 'user:pass1', 'user:pass2', 'user:pass3', etc.

Example 2: Multiple failed PINs are attempted for the same customer account.

Example 3: In an online banking application, several invalid mobile authentication codes, transaction verification codes or transaction authentication numbers are submitted.

Example 4: A user provides the correct password, but repeatedly fails to provide the required second password correctly.

Code

[Java] [.Net] [PHP]

AE3: High Rate of Login Attempts

ID

AE3

Title

High Rate of Login Attempts

Category

AuthenticationException

Description

The rate of login attempts becomes too high (possibly indicating an automated login attack).

Considerations

The threshold should relate to a limit and period appropriate to the application (e.g. total number in a second or minute or hour).

Tuning

-

Examples

User sends the following login attempts within 1 second - 'user1:pass1', 'user1:pass2', 'user2:pass3', 'user2:pass4'.

Code

[Java] [.Net] [PHP]

AE4: Unexpected Quantity of Characters in Username

ID

AE4

Title

Unexpected Quantity of Characters in Username

Category

AuthenticationException

Description

The user provides a username with a large number of characters.

Considerations

-

Tuning

(same as RE7)

Examples

The user sends a username that is 200 characters long when 6-8 are expected.

Code

[Java] [.Net] [PHP]

AE5: Unexpected Quantity of Characters in Password

ID

AE5

Title

Unexpected Quantity of Characters in Password

Category

AuthenticationException

Description

The user provides a password with a large number of characters.

Considerations

Higher limits may be required for sites which allow users to have pass phrases.

Tuning

(same as RE7)

Examples

Example 1: The user sends a password that is 200 characters long, when 5-20 are expected.

Example 2: The user sends a PIN of 30 characters.

Code

[Java] [.Net] [PHP]

AE6: Unexpected Type of Character in Username

ID

AE6

Title

Unexpected Type of Character in Username

Category

AuthenticationException

Description

The user provides a username which contains characters outwith the expected range.

Considerations

Any characters below hex value 20 or above 7E are often considered illegal (decimal values of below 32 or above 126).

Tuning

Users may be confused between a username, customer identification code and their account number, or even between offline and online identifiers. Mis-typing might add a character like "]" or "#" if these are adjacent to the ENTER/CR key. Whitespace may be appended to values when copied from a spreadsheet cell (e.g. a line feed character when cell values are copied and pasted from Excel). A password may be put in the username field by accident.

Examples

The user sends a username that contains ASCII non-printable characters such as the NULL byte.

Code

[Java] [.Net] [PHP]

AE7: Unexpected Type of Character in Password

ID

AE7

Title

Unexpected Type of Character in Password

Category

AuthenticationException

Description

The user provides a password containing characters outwith the expected range.

Considerations

Examples include null byte, and characters which need the ALT key to be used.

Tuning

(same as AE6)

Examples

The user sends a password that contains ASCII characters below 20 or above 7E.

Code

[Java] [.Net] [PHP]

AE8: Providing Only the Username

ID

AE8

Title

Providing Only the Username

Category

AuthenticationException

Description

The user submits a POST request which only contains the username variable. The password variable has been removed.

Considerations

This is different from only providing the username in the login form since in that case the password variable would be present and empty.

Tuning

-

Examples

The user utilizes a proxy tool to remove the password variable from the submitted POST request.

Code

[Java] [.Net] [PHP]

AE9: Providing Only the Password

ID

AE9

Title

Providing Only the Password

Category

AuthenticationException

Description

The user submits a POST request which only contains the password variable. The username variable has been removed.

Considerations

This is different from only providing the password in the login form since in that case the username variable would be present and empty.

Tuning

-

Examples

The user utilizes a proxy tool to remove the username variable from the submitted POST request.

Code

[Java] [.Net] [PHP]

AE10: Additional POST Variable

ID

AE10

Title

Additional POST Variable

Category

AuthenticationException

Description

Additional, unexpected POST variables are received during an authentication request.

Considerations

-

Tuning

(same as RE5)

Examples

The user utilizes a proxy tool to add the POST variable of 'admin=true' to the request.

Code

[Java] [.Net] [PHP]

AE11: Missing POST Variable

ID

AE11

Title

Removing POST Variables

Category

AuthenticationException

Description

Expected POST variables are not present within the submitted authentication request.

Considerations

-

Examples

The user utilizes a proxy tool to remove an additional POST variable, such as 'guest=true', from the POST request.

Tuning

(same as RE6)

Code

[Java] [.Net] [PHP]

AE12: Utilization of Common Usernames

ID

AE12

Title

Utilization of Common Usernames

Category

AuthenticationException

Description

Common dictionary usernames are used to attempt to log into the application.

Considerations

-

Tuning

Common usernames might be allowed during self-registration or when editing account details.

Examples

Log in attempted with usernames "administrator", then "admin", then "test"

Code

[Java] [.Net] [PHP]

SessionException

SE1: Modifying Existing Cookie

ID

SE1

Title

Modifying Existing Cookie

Category

SessionException

Description

A request is received containing a cookie with a modified value.

Considerations

This could be determined if the cookie is modified to an illegal value.

Tuning

In a poorly designed application, the length of the cookie value, or the combined size of all the cookies, might possibly exceed that which is supported.

Examples

Example 1: The user utilizes a proxy tool to change the encrypted cookie to an alternative value which does not properly decode within the application.

Example 2: The user modifies an unencrypted cookie and sets an illegal value for a particular variable.

Code

[Java] [.Net] [PHP]

SE2: Adding New Cookie

ID

SE2

Title

Adding New Cookie

Category

SessionException

Description

A request is received which contains additional cookies that are not expected by the application.

Considerations

A session cookie existing when it should not (e.g. prior to authentication) is probably indicative of an attack. But cookies may also be set by third party sites which get send with the request - these may be harmless. Also consider what other applications exist on sub-domains (e.g. www.example.com, extranet.example.com and sales.example.com) which may also be setting cookies.

Tuning

-

Examples

The user utilizes a proxy tool to add cookies to the request.

Code

[Java] [.Net] [PHP]

SE3: Deleting Existing Cookie

ID

SE3

Title

Deleting Existing Cookie

Category

SessionException

Description

A request is received which does not contain the expected cookies.

Considerations

The user may have bookmarked a page they had visited during a previous authenticated session.

Tuning

In a poorly designed application, the number of cookies might exceed the allowed number supported by the user's browser.

Examples

The user utilizes a proxy tool to remove cookies or portions of cookies from a request.

Code

[Java] [.Net] [PHP]

SE4: Substituting Another User's Valid Session ID or Cookie

ID

SE4

Title

Substituting Another User's Valid Session ID or Cookie

Category

SessionException

Description

A request is received which contains cookie data that is clearly from another user or another session.

Considerations

-

Tuning

A mis-configured proxy might send the same session ID or cookie for all users.

Examples

The user utilizes a proxy tool to substitute valid data from another user or session into the cookie. An example would be changing some sort of identification number within the cookie.

Code

[Java] [.Net] [PHP]

SE5: Source Location Changes During Session

ID

SE5

Title

Source Location Changes During Session

Category

SessionException

Description

Valid requests, containing valid session credentials, are received from multiple source locations indicating a possible session hijacking attack.

Considerations

A full IP address may not be constant for some users during normal use. Enforcing single fixed IP addresses for each session in an intranet application may be valid. However, if the application is accessible over public networks, changing IP address cannot be excluded and it may be more useful to consider fixing just part of the IP address, or looking for more significant changes such as when the user's IP address geo-location region or country changes (see Autonomous System Number (ASN) and Detecting Malice with ModSecurity: GeoLocation Data). Note: source port number should not be used in checks since this usually changes very frequently.

Tuning

If the full IP address is used for this, it may change slightly from request to request by the same user.

Examples

User A's session is compromised and User B begins using the account. The requests originating from User B will possibly contain a different source IP address the User A. The source IP addresses could be the same if both users where behind the same NAT.

Code

[Java] [.Net] [PHP]

SE6: Change of User Agent Mid Session

ID

SE6

Title

Change of User Agent Mid Session

Category

SessionException

Description

The User-Agent value of the header changes during a session. This indicates a different browser is now being used. Although this value is under the control of the sender, a change in this may indicates that the session has been compromised and is being used another individual. This will likely not be the case that the user has simply copied and pasted the URL from one browser to another on the same system because this action would not copy over the appropriate session identifiers.

Considerations

Optionally also include other HTTP headers in this check. For example, the Accept-Encoding and Accept-Language headers do not normally change and could be concatenated with the User-Agent and hashed to created an identifier.

The ideas described in Panopticlick and Javascript Browser Fingerprinting can also be used to fingerprint a particular client system but require the use of client-side code. Application owners should check the legality of collecting data, and whether it is considered "personal data" which may have additional constraints in some jurisdictions.

Tuning

-

Examples

Midsession, the UserAgent changes from Firefox to Internet Explorer.

Code

[Java] [.Net] [PHP]

AccessControlException

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

ID

ACE1

Title

Modifying URL Argument Within a GET for Direct Object Access Attempt

Category

AccessControlException

Description

The application is designed to use an identifier for a particular object, such as using categoryID=4 or user=guest within the URL. A user modifies this value in an attempt to access unauthorized information. This exception should be thrown anytime the identifier received from the user is not authorized due to the identifier being nonexistent or the identifier not authorized for that user.

Considerations

-

Tuning

Bookmarking , truncation, and mistyping issues could lead to some access control exceptions.

Examples

The user modifies the following URL from

example.com/viewpage?page=1&user=guest

to

example.com/viewpage?page=22&user=admin

Code

[Java] [.Net] [PHP]

ACE2: Modifying Parameter Within A POST for Direct Object Access Attempt

ID

ACE2

Title

Modifying Parameter Within A POST for Direct Object Access Attempt

Category

AccessControlException

Description

The value of a non-free text html form element (i.e. drop down box, radio button) is modified to an illegal value. The value either does not exist or is not authorized for the user.

Considerations

-

Tuning

(same as ACE1 for bookmarking)

Examples

The user utilizes a proxy tool to intercept a POST request and changes the submitted value to a value that was not available through the normal display. For example, the user encounters a dropdown box containing the numbers 1 through 10. The user selects 5 and then intercepts the request to change the submitted value to 100.

Code

[Java] [.Net] [PHP]

ACE3: Force Browsing Attempt

ID

ACE3

Title

Force Browsing Attempt

Category

AccessControlException

Description

An authenticated or unauthenticated user sends a request for a non-existent resource (e.g. page, directory listing, image, file, etc), or a resource that is not authorized for that user.

Considerations

-

Tuning

Requests for non-existent resources may occur for many reasons such as Benign Unexpected URLs - Part 1 - Missing (404 Not Found Error) Files

Examples

Example 1: The user is authenticated and requests site.com/PageThatDoesNotExist

Example 2: The user is authenticated and requests a video they are not authorized to download/view

Example 3: An unauthenticated user (perhaps with a session ID) requests a listing of a directory detailed in the site's robots.txt file

Code

[Java] [.Net] [PHP]

ACE4: Evading Presentation Access Control Through Custom POST

ID

ACE4

Title

Evading Presentation Access Control Through Custom POST

Category

AccessControlException

Description

A POST request is received which is not authorized for the current user and the user could not have performed this action without crafting a custom POST request.

Considerations

This situation is most likely to occur when presentation layer access controls are in place and have removed the user's ability to initiate the action through the presentation of the application. An attacker may be aware of the functionality and attempt to bypass this presentation layer access control by crafting their own custom message and sending this in an attempt to execute the functionality.

Tuning

-

Examples

The application contains the ability for an administrator to delete a user. This method is normally invoked by entering the username and submitting to https://oursite/deleteuser Presentation layer access controls ensure the delete user form is not displayed to non-administrator users. A malicious user has access to a non-administrator account and is aware of the delete user functionality. The malicious user sends a custom crafted POST message to https://oursite/deleteuser in an attempt to execute the delete user method.

Code

[Java] [.Net] [PHP]

InputException

IE1: Cross Site Scripting Attempt

ID

IE1

Title

Cross Site Scripting Attempt

Category

InputException

Description

The HTTP request contains common XSS attacks which are often used by attackers probing for XSS vulnerabilities.

Considerations

Detection should be configured to test all GET and POST values as well as all header names and values for the following values.

Tuning

There are many patterns which could be XSS but may also be normal user input to a free text field e.g. "Press the 'drop' button" if a pattern were looking for a single quotation mark followed by SQL commands like DROP, INSERT, UPDATE and DELETE. Applications that are used to discuss or share information about programming, software development and security may want to allow such free text input, provided it is encoded/escaped correctly.

Examples

The user utilizes a proxy tool to add an XSS attack to the header value and the 'displayname' POST variable. The header value could be displayed to an admin viewing log files and the 'displayname' POST variable may be stored in the application and displayed to other users. Note, the following XSS attacks would only be used by an attacker to probe for vulnerability. An actual XSS attack would be customized by the attacker.

<script>alert(document.cookie);</script> <script>alert();</script> alert(String.fromCharCode(88,83,83)) <IMG SRC="javascript:alert('XSS');"> <IMG SRC=javascript:alert('XSS')> <IMG SRC=javascript:alert(&quot;XSS&quot;)> <BODY ONLOAD=alert('XSS')>

Cross references:

  • OWASP ModSecurity Core Rule Set Project v2.0.5
    • (41) XSS Attacks: Cross-site Scripting (XSS) Attack (67 Rules)
    • (41) XSS Attacks: Cross-site Scripting (XSS) Attack [Paranoid Mode] (Additional 67 Rules)
Code

[Java] [.Net] [PHP]

IE2: Violation Of Implemented White Lists

ID

IE2

Title

Violation Of Implemented White Lists

Category

InputException

Description

The application receives user-supplied data that violates an established white list validation.

Considerations

See AC3 (Force Browsing Attempts) about requests for non-existent/unauthorised (i.e. not white listed) URLs.

Tuning

(same as IE1)

Examples

The user submits data that is not correct for the particular field. This may not be attack data necessarily, but repeated violations could be an attempt by the attacker to determine how an application works or to discover a flaw.

Code

[Java] [.Net] [PHP]

IE3: Violation Of Implemented Black Lists

ID

IE3

Title

Violation Of Implemented Black Lists

Category

InputException

Description

The application receives user-supplied data that violates an established black list validation.

Considerations

-

Tuning

(same as IE1)

Examples

The application receives user-supplied data that violates an established black list validation. This may not be attack data necessarily, but repeated violations could be an attempt by the attacker to determine how an application works or to discover a flaw or to exploit a flaw. This black list approach suffers from the potential for greater false positives than IE2 above, and cannot be used to identify all potential malicious data.

Example 1: URL in comment field identified as suspected phishing and malware pages using Google Safe Browsing API)

Example 2: Parameter value matches a known SQL injection pattern.

Example 3: Parameter value matches a known XSS pattern.

Code

[Java] [.Net] [PHP]

IE4: Violation of Input Data Integrity

ID

IE4

Title

Violation of Input Data Integrity

Category

InputException

Description

The application receives HTTP header or body parameter values which have been tampered with when no change should have occurred.

Considerations

-

Tuning

This detection point should only be used with parameters that cannot be altered by accident. Input types text and textarea would not normally be suitable, even if the elements are disabled in the browser. Be wary of assuming JavaScript will prevent modification of form elements in all conditions.

Examples

Example 1: Hidden form field modified by client.

Example 2: Select list value submitted in response, not sent by server as an available option value.

Example 3: Cookie set by server has been manipulated by the client.

Example 4: Cookie created by client instead of by the server.

Code

[Java] [.Net] [PHP]

IE5: Violation of Stored Business Data Integrity

ID

IE5

Title

Violation of Stored Business Data Integrity

Category

InputException

Description

User's input leads to violation of data integrity.

Considerations

-

Tuning

-

Examples

Example 1: A user's action leads to a system integrity error when writing to, or updating, a database.

Example 2: Business rule checks detect that a user's action is not compatible.

Example 3: Data accuracy checking detects duplicate records for a user.

Example 4: User input leads to an unexpected file change (e.g. .htaccess file overwritten, page template changed).

Example 5: User's request leads to a new, unexpected, outbound network connection being made (e.g. mail sent to an SMTP server, files downloaded from a FTP server).

Code

[Java] [.Net] [PHP]

IE6: Violation of Security Log Integrity

ID

IE6

Title

Violation of Security Log Integrity

Category

InputException

Description

Security or audit log tampering detected.

Considerations

AppSensor may rely on the accuracy of "log" data to make decisions when thresholds are reached. This detector aims to detect the insertion of forged entries, corruption of logs, unauthorised deletion of and changes to records.

See also:

Tuning

-

Examples

Example 1: Special characters embedded in logged data about a user's activity cause the data to overwrite a previous log entry.

Example 2: Log file integrity is broken by modification to an existing log entry.

Code

[Java] [.Net] [PHP]

EncodingException

EE1: Double Encoded Character

ID

EE1

Title

Double Encoded Characters

Category

EncodingException

Description

An HTTP request is received which contains one or more double encoded values.

Considerations

-

Tuning

Data supplied by other party systems may have encoding issues.

Examples

The user sends encodes the % symbol to %25 and appends 3C. The user is sending %253C which may be interpreted by the application as %3C which is actually <.

Code

[Java] [.Net] [PHP]

EE2: Unexpected Encoding Used

ID

EE2

Title

Unexpected Encoding Used

Category

EncodingException

Description

An HTTP request is received which contains values that have encoded in an unexpected format.

Considerations

-

Tuning

(same as EE1)

Examples

The user encodes an attack such as alert(document.cookie) into the UTF-7 format and sends this data the application. This could bypass validation filters and be rendered to a user in certain situations.

Cross references:

  • OWASP ModSecurity Core Rule Set Project v2.0.5
    • (20) Protocol Violations: UTF8 Encoding Abuse Attack Attempt (950801)
    • (30) HTTP Policy Enforcement: Request Content Type Is Not Allowed by Policy (960010)
Code

[Java] [.Net] [PHP]

CommandInjectionException

CIE1: Blacklist Inspection for Common SQL Injection Values

ID

CIE1

Title

Blacklist Inspection for Common SQL Injection Values

Category

CommandInjectionException

Description

A request is received which contains common SQL injection attack attempts.

Considerations

The point of this detection is not to detect all variations of a SQL injection attack, but to detect the common probes which an attacker or tool might use to determine if a SQL injection vulnerability is present. Unless the site contains some sort of message board for discussing SQL injection, there is little reason that the SQL injection examples should ever be received from a user request.

Tuning

(same as IE1)

Examples

The user sends a request and modifies a URL parameter from category = 5 to category = 5' OR '1' = '1 in an attempt to perform an SQL injection attack. The user could perform similar attacks by modifying POST variables or even the request headers to contain SQL injection attacks. ' OR '1'='1 ' OR 'a'='a ' OR 1=1-- xp_cmdshell UNION JOIN

Cross references:

Code

[Java] [.Net] [PHP]

CIE2: Detect Abnormal Quantity of Returned Records

ID

CIE2

Title

Detect Abnormal Quantity of Returned Records

Category

CommandInjectionException

Description

A database query is executed which returns more records than expected.

Considerations

-

Tuning

-

Examples

Example 1: A query of a non-SQL dataset should only return 1 record but 100 records are returned.

Example 2: The application is designed to allow a user to maintain 5 profiles. A user makes a request to view all of their profiles. The database SQL query, which is expected to always return 5 or less results, returns 10,000 records. Something in the application, or user's actions, has caused unauthorized data to be returned.

Example 3: Extraction of data from an XML file should only return one matching node, but more than one is returned.

Code

[Java] [.Net] [PHP]

CIE3: Null Byte Character in File Request

ID

CIE3

Title

Null Byte Character in File Request

Category

CommandInjectionException

Description

A request is received to download a file from the server. The filename requested contains the null byte the file name. This is an attempted OS injection attack.

Considerations

-

Tuning

-

Examples

The user modifies the filename of the requested file to download to contain the null byte. The null byte can be added by inserting the hex value %00.

Cross references:

Code

[Java] [.Net] [PHP]

CIE4: Carriage Return or Line Feed Character in File Request

ID

CIE4

Title

Carriage Return or Line Feed Character in File Request

Category

CommandInjectionException

Description

A request is received which contains the carriage return or line feed characters within the POST data or the URL parameters. This is an attempted HTTP split response attack.

Considerations

-

Tuning

-

Examples

The user includes the hex value %0D or %0A in the HTTP request POST data or URL parameters.

Cross references:

Code

[Java] [.Net] [PHP]

FileIOException

FIO1: Detect Large Individual File

ID

FIO1

Title

Detect Large Individual File

Category

FileIOException

Description

A file upload feature detects that a large file has been submitted for upload which exceeds the maximum upload size.

Considerations

-

Tuning

-

Examples

The user attempts to upload a large file to occupy resources or fill up disk space.

Code

[Java] [.Net] [PHP]

FIO2: Detect Large Number of File Uploads

ID

FIO2

Title

Detect Large Number of File Uploads

Category

FileIOException

Description

A user uploads an excessively large number of files.

Considerations

The limit and period used to determine the threshold rate is application dependent, and may also depend on the user's role.

Tuning

-

Examples

A single user attempts to upload multiple small files to occupy resources or fill up disk space.

Code

[Java] [.Net] [PHP]

Honey Trap

HT1: Alteration to Honey Trap Data

ID

HT1

Title

Alteration to Honey Trap Data

Category

HoneyTrap

Description

Fake (not otherwise needed by the application) data sent to the user and returned (e.g. as form, URL, cookie values or in the path or HTTP header) is modified. This is usually combined with making the name or value a tempting item for an attacker to try modifying.

Considerations

Similar techniques can also be used for the creation of accessible CAPTCHA.

See also ideas at http://blogs.sans.org/appsecstreetfighter/2009/06/04/my-top-6-honeytokens/

Tuning

-

Examples

Example 1: Otherwise useless hidden fields, which look like potential vulnerabilities, added to some forms are sent back to the server modified (e.g. <input type="hidden" name="admin" value="false" />).

Example 2: An additional URL parameter, which is not used by the application, is modified by the user (e.g. www.example.com/account.jsp?debug=0).

Example 3: An additional fake cookie is added and is modified by the user.

Example 4: URL rewriting is used and a fake directory name is added; this is modified by the user (e.g. www.example.com/orders/normaluser/display.php).

Code

[Java] [.Net] [PHP]

HT2: Honey Trap Resource Requested

ID

HT2

Title

Honey Trap Resource Requested

Category

HoneyTrap

Description

A purposely leaked resource that has no use in normal application use is requested by a user.

Considerations

Ensure the resource is not linked from normal application content such that a spider or robot might find the resource in any case.

Tuning

-

Examples

Example 1: Page, directory or other resource listed in the application's robots.txt robots exclusion file is requested by the user.

Example 2: URL identified only in HTML comments is requested by the user.

Example 3: Unexposed server function call included in Flash file source code is requested by the user.

Code

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HT3: Honey Trap Data Used

ID

HT3

Title

Honey Trap Data Used

Category

HoneyTrap

Description

Special data sent or accessed by a user.

Considerations

For honey trap data that is detected on egress only, use of outbound content monitoring (e.g. a web application firewall or similar technique) may be helpful.

Tuning

-

Examples

Example 1: Fake user name and password only visible in source HTML code used to attempt to log in to the application (e.g. in HTML comments, in server-side code 'accidentally' delivered to the user).

Example 2: A special code number or account name is left in a discussion forum site; this is then used in the application.

Example 3: An attempt is made to authenticate with the user name listed in the first row (e.g. ID=1) of the application's database table of Users.

Example 4: Data from a fake account record is sent by the server and detected; this record should not normally be accessible by anyone using the application.

Code

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UserTrendException

UT1: Irregular Use of Application

ID

UT1

Title

Irregular Use of Application

Category

UserTrendException

Description

The application receives an unusual pattern of requests for the same page or feature from a user. The user may be sending different data combinations or trying to detect errors in the page.

Considerations

-

Tuning

Use of bookmarked URLs and the "back" button might generate out-of-sequence requests. See also related frequency of feature use in UT4.

Examples

Example 1: The user requests a particular page, such as the address update page, numerous times.

Example 2: The user requests a page out-of-sequence, such as an intermediate step in a multi-stage form.

Example 3: The user only requests dynamic content, and not the associated static files (e.g. images, stylesheets).

Code

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UT2: Speed of Application Use

ID

UT2

Title

Speed of Application Use

Category

UserTrendException

Description

The speed of requests from a user indicates that an automated tool is being used to access the site. The use of a tool undertaking a high number of requests quickly may indicate reconnaissance for an attack or attempts to identify vulnerabilities in the site. Slow usage (e.g. between account creation and use) might indicate automated account creation that are then used subsequently for attacks.

Considerations

If enforced inappropriately or too rigorously, this detection point could lead to false positives.

Tuning

Time periods need to be set broadly enough to cater for the normal spread in user behavior. Some users may use automated tools that store passwords securely to populate and submit authentication forms.

Examples

Example 1: The user utilizes an automated tool to request hundreds of pages per minute.

Example 2: The user does not log in to the site until a long time after their account is created.

Example 3: New (uncached) static content such as images and style sheets associated with each page are not requested in a similar time period as the page.

Example 4: A CAPTCHA challenge is responded to more quickly than a human could possibly do.

Code

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UT3: Frequency of Site Use

ID

UT3

Title

Frequency of Site Use

Category

UserTrendException

Description

Change in how often the site is used by a user

Considerations

-

Tuning

Some users may correctly change their behavior in the frequency of accessing the application.

Examples

The user normally accesses the site 1 per week, but this changes to many times per day.

Code

[Java] [.Net] [PHP]

UT4: Frequency of Feature Use

ID

UT4

Title

Frequency of Feature Use

Category

UserTrendException

Description

The rate of a user utilizing a particular application feature changes dramatically.

Considerations

-

Tuning

It may be valid for some functionality may be requested repeatedly. For example a real customer placing many orders, a press officer publishing a backlog of press releases, or an administrator populating a staff directory.

Examples

Example 1: The user submits many forum messages in a short period of time.

Example 2: The user adds many new friends rapidly.

Code

[Java] [.Net] [PHP]

SystemTrendException

STE1: High Number of Logouts Across The Site

ID

STE1

Title

High Number of Logouts Across The Site

Category

SystemTrendException

Description

A sudden spike in logouts across the application could indicate a XSS and CSRF attack placed within the application which is automatically logging off users.

Considerations

-

Tuning

-

Examples

The hourly usage of the log-off feature of the application suddenly spikes by 500%.

Code

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STE2: High Number of Logins Across The Site

ID

STE2

Title

High Number of Logins Across The Site

Category

SystemTrendException

Description

A sudden spike in logins across the application could indicate users being redirected to the site from a phishing email looking to exploit a XSS vulnerability in the site.

Considerations

-

Tuning

-

Examples

The hourly usage of the logon feature of the application suddenly spikes by 1,000%.

Code

[Java] [.Net] [PHP]

STE3: Significant Change in Usage of Same Transaction Across The Site

ID

STE3

Title

Significant Change in Usage of Same Transaction Across The Site

Category

SystemTrendException

Description

A sudden spike in similar activity across numerous users of the application may indicate a phishing attack or CSRF attack against the users; a rapid reduction in activity may indicate users are being redirected elsewhere; a significant change in average transaction value or other quantitative measure may indicate suspicious activity.

Considerations

External events (e.g. a news item) may lead to additional unexpected traffic which is not an attack.

Tuning

A special requirement, situation or event may dramatically change the rate of use of certain transactions. (See also UT4)

Examples

Example 1: The hourly usage of the update email address feature of the application suddenly spikes by 2,000%.

Example 2: A website is compromised and users are redirected to a malicious site part-way through a process; the number of successful fully completed transactions drops to nil.

Code

[Java] [.Net] [PHP]

Reputation

These reputation detection points could be treated either as:

  • like any other detection point contributing to the count of suspicious events, or
  • used to alter security logging, or the threshold levels, or associated response actions

The former could lead to a much higher false positive rate.

RP1: Suspicious or Disallowed User Source Location

ID

RP1

Title

Suspicious or Disallowed User Source Location

Category

Reputation

Description

The user is identified as using an IP address associated with a blacklist

Considerations

Suspicious or invalid geo-location, IP addresses or IP address ranges may be identified using a whitelist,internal blacklist, list of Tor nodes (e.g. https://torstat.xenobite.eu/), HTTP blacklist (e.g. http://www.projecthoneypot.org/httpbl.php and Dshield http://www.dshield.org) list of spammers (e.g. Spamhaus http://www.spamhaus.org/) or known botnets (e.g. http://www.shadowserver.org/wiki/).

"Suspicious" may also depend upon the type of user e.g. users in the "CMS manager" role should be using an internal network IP address, public users could be from anywhere, customers should only be accessing the application from a particular geographical region, search engine robots should be from a limited range of IP addresses.

Take care that "suspicious" does not contribute to greater false positives.

Tuning

The currency and accuracy of needs to be considered when the information is used in AppSensor. The method of challenge and removal of inaccuracies, and the speed of this process, should also be considered.

Examples

Example 1: A user with an external IP address is accessing an internal application, which should not be occurring.

Example 2: An authenticated user is accessing the application using a known Tor node, and attack detection thresholds are made more strict.

Example 3: An authenticated user is accessing the application from a known trustworthy IP address, and thresholds for certain activity (e.g. input data validation errors) are relaxed slightly.

Example 4: The IP address of the payment authentication server, used by the application for credit card authorisation, changes.

Code

[Java] [.Net] [PHP]

RP2: Suspicious External User Behavior

ID

RP2

Title

Suspicious External User Behavior

Category

Reputation

Description

External (to the application) devices and systems (e.g. host and network IDS, file integrity monitoring, disk usage monitoring, anti-malware service, IPS, network firewall, web application firewall, web server logging, XML gateway, database firewall, SIEM) detect anomalous behavior by the user (e.g. session and/or IP address).

This information can be used by the application to contribute to its knowledge about a potential attacker. In some cases, the information could be detected by the application itself (e.g. XSS pattern black listing), but may be more effectively identified by the external device, or is not known to the application normally (e.g. requests for missing resources that the web server sees, but does not pass onto the application).

Considerations

The greater the knowledge a device or system has about the application, the greater confidence can be given to evidence of suspicious behaviour. Therefore, for example, attempted SQL injection detected by a web application firewall (WAF) might be given greater weight than information from a network firewall about the IP address.

The power of AppSensor is its accuracy and low false positive rate, and the usage of external data should be carefully assessed to ensure it does not contribute to a higher false positive rate.

Tuning

The level of trust in information from the external device/system/organization needs to be considered.

Examples

Example 1: An IDS has detected suspicious activity by a particular IP address, and this is used to temporarily tighten the attack detection thresholds for requests from all users in the same IP address range.

Example 2: An application is using the ModSecurity web application firewall with the Core Rule Set, and utilises the anomaly score data passed forward in the X-WAF-Events and X-WAF-Score HTTP headers (optional rules in modsecurity_crs_49_header_tagging.conf) to adjust the level of application logging for each user.

Example 3: Information from an instance of PHPIDS suggests request data may be malicious.

Code

[Java] [.Net] [PHP]

RP3: Suspicious Client-Side Behavior

ID

RP3

Title

RP3 Suspicious Client-Side Behavior

Category

Reputation

Description

The application receives a report of client-side security policy exceptions.

Considerations

Take care this information does not contribute to greater false positives.

Tuning

-

Examples

Example 1: An internal corporate intranet application detects use of a non-standard workstation configuration (e.g. using JavaScript font or plugin detection see SE6). An alert is raised for further investigation.

Example 2: An online banking application receives details of suspicious client-side behaviour that would not be expected in normal application use, via a Content Security Policy violation report. The application increases logging for the user, and decreases the monetary limit at which the user's payments require manual authorisation by bank staff.

Example 3: The HTTP user agent header value does not agree with other indicators (e.g. using JavaScript detection as in example 1 above). Reference.

Example 4: A honeyclient system monitoring the web application reports unexpected behavior in the generated web pages output.

Example 5: A third-party monitoring system detects page content that is unauthorised and/or contrary to policy (e.g. structure, included links, HTML validation, inclusion of certain data such as payment card data).

Code

[Java] [.Net] [PHP]

RP4: Change to Environment Threat Level

ID

RP4

Title

Change to Environment Threat Level

Category

Reputation

Description

The general threat level (e.g. general risk of attack from the Internet, or specific targetted attacks against an organisation) is elevated. This could also be used to change response sensitivity due to short-term effects such as application upgrades/patching.

Considerations

This input could be used to alter thresholds for AppSensor responses.

Tuning

The detection point could receive specially crafted input from an attacker, and therefore the information should be considered as untrusted.

Examples

Example 1: A machine-readable threat index is read from a third-party and is used to control security logging levels.

Example 2: Business circumstances (e.g. increased attention by activists) raises the suspicion the application may be at increased risk of mis-use, and response thresholds for attack detection are tightened for non-authenticated users.

Example 3: The Defense Condition Level (DEFCON) is raised and response thresholds are changed

Code

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