OWASP Risk Rating Methodology

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OWASP Testing Guide v2 Table of Contents

Risk is typically defined as a product of the effective Threat, Vulnerability and associated Cost of recovery. For the purposes of a Security Assessment, OWASP defines the risk associated with a security finding as a product of the impact, ease of exploitation, exposure and nominal value of the asset.

Risk = Impact x Ease of Exploitation x Exposure x Nominal Value

In breaking down the security findings in this way, they and their implications may be better evaluated, prioritised and managed.

Impact is taken as a measure of the implications on the discrete component should it be compromised. This is taken out of the context of the nature of the application or host (e.g. server, firewall or workstation), and regardless of the type of data stored on it.

The threat component is in part measured through Ease of Exploitation which quantifies the potential of an attacker taking advantage of the flaw to violate system integrity.

Exposure quantifies the likelihood that the vulnerability can be compromised through its availability. For example, an easily exploited vulnerability on an Internet facing host would be highly exposed, and therefore very likely to be compromised. An internal host with a vulnerability that was difficult to exploit would present a much lower threat. For example, a vulnerability on an Internet facing host would be highly exposed, and therefore very likely to be compromised. An internal host with the same vulnerability would present a much lower threat.

The final part of the risk equation is the Nominal Value of the elements in your environment, based on the importance of the system and its data. The testing team can estimate the importance of the host based on information given and the context, but clients are encouraged to consider the importance of hosts based on business criteria & asset value.

Risk Categories:

• Impact (imp)
• critical
• high
• medium
• low

Ease of Exploitation (EoE)

• Easy
• Moderate
• Difficult

Exposure (Exp)

• Very high
• High
• Medium
• Low

Nominal Value (Val)

• High
• Medium
• Low

Putting this into practice looks like

Vulnerability found: Session handling inadequate

• Imp: Medium
• EoE: Moderate
• Exp: Very High
• Val: High

Resulting in OWASP Risk Rating: ??? (tbd)

Category	Ref Number	Name	Finding	Affected Item	Comment/Solution	Risk Value
Information Gathering		Application Discovery
		Spidering and googling
		Analisys of error code
		SSL/TLS Testing
		DB Listener Testing
		File extensions handling
		Old, backup and unreferenced files
Business logic testing
Authentication Testing		Default or guessable account
		Brute Force
		Bypassing authentication schema
		Directory traversal/file include
		Vulnerable remember password and pwd reset
		Logout and Browser Cache Management Testing
Session Management Testing		Session Management Schema
		Session Token Manipulation
		Exposed Session Variables
		Session Riding
		HTTP Exploit
Data Validation Testing		Cross site scripting
		HTTP Methods and XST
		SQL Injection
		Stored procedure injection
		ORM Injection
		LDAP Injection
		XML Injection
		SSI Injection
		XPath Injection
		IMAP/SMTP Injection
		Code Injection
		OS Commanding
		Buffer overflow
		Incubated vulnerability
Denial of Service Testing		Locking Customer Accounts
		User Specified Object Allocation
		User Input as a Loop Counter
		Writing User Provided Data to Disk
		Failure to Release Resources
		Storing too Much Data in Session
Web Services Testing		XML Structural Testing
		XML content-level Testing
		HTTP GET parameters/REST Testing
		Naughty SOAP attachments
		Replay Testing
AJAX Testing		AJAX Vulnerabilities

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OWASP Testing Guide v2

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