TRA (Threat and Risk Assessment) & Two Examples (Quantitative & Qualitative)

A Threat and Risk Assessment analyzes a software or hardware system for vulnerabilities, examines potential threats associated with those vulnerabilities, and evaluates the resulting security risks. A vulnerability is any “flaw or weakness in system security procedures, design, implementation, or internal controls that could be exercised (accidentally triggered or intentionally exploited) and result in a security breach or a violation of the system's security policy” (NIST SP800-30 Risk Management Guide for Information Technology Systems). The level of threat is determined from the potential for any natural, human or environmental source to trigger or exploit any identified vulnerability. The risk assessment looks at both the probability of that threat occurring, and the impact on both system and organization should it occur. An appropriate strategy can then be formulated for each risk depending on severity (such as acceptance of the risk, adoption of a mitigation plan, or implementation of an avoidance strategy).

Define TRA Methodology

NIST SP 800-30 Rev. 1 - Guide for Conducting Risk Assessments
FIPS 200 - Minimum Security Requirements for Federal Information and Information Systems
FIPS 199 - Standards for Security Categorization of Federal Information and Information Systems



Define Process

Based on FIPS 200, the generalized format for expressing the security category (SC) of an information system is:
SC information system = {(confidentiality, impact), (integrity, impact), (availability, impact)},
where the acceptable values for potential impact are low, moderate, or high.

Since the potential impact values for confidentiality, integrity, and availability may not always be the same for a particular information system, the high water mark concept must be used to determine the overall impact level of the information system.


Define Scope

Organizations must meet the minimum security requirements in this standard by selecting the appropriate security controls and assurance requirements as described in NIST Special Publication 800-53, Recommended Security Controls for Federal Information Systems

The selected set of security controls must include one of three, appropriately tailored8 security control baselines from NIST Special Publication 800-53 that are associated with the designated impact levels of the organizational information systems as determined during the security categorization process. - For low-impact information systems, organizations must, as a minimum, employ appropriately tailored security controls from the low baseline of security controls defined in NIST Special Publication 800-53 and must ensure that the minimum assurance requirements associated with the low baseline are satisfied. - For moderate-impact information systems, organizations must, as a minimum, employ appropriately tailored security controls from the moderate baseline of security controls defined in NIST Special Publication 800-53 and must ensure that the minimum assurance requirements associated with the moderate baseline are satisfied. - For high-impact information systems, organizations must, as a minimum, employ appropriately tailored security controls from the high baseline of security controls defined in NIST Special Publication 800-53 and must ensure that the minimum assurance requirements associated with the high baseline are satisfied.

Example One - Quantitative TRA

Step #1: Identify and Prioritize Assets

Step #2: Identify Threats

Step #3: Identify Vulnerabilities

Step #4: Analyze Controls

Step #5: Determine the Likelihood of an Incident

Step #6: Assess the Impact a Threat Could Have

Step #7: Prioritize the Information Security Risks

Step #8: Recommend Controls

Step #9: Document the Results

A useful tool for estimating risk in this manner is the risk-level matrix. A high likelihood that the threat will occur is given a value of 1.0; a medium likelihood is assigned a value of 0.5; and a low likelihood of occurrence is given a rating of 0.1. Similarly, a high impact level is assigned a value of 100, a medium impact level 50, and a low impact level 10. Risk is calculated by multiplying the threat likelihood value by the impact value, and the risks are categorized as high, medium or low based on the result.

For example:
For Malicious human - DDOS attack with Firewall vulnerability on Website asset:
Threat = high =100 (1,50,100,120)
Vulnerability = low = 0.1 (0.1,0.5,1)
Asset = Critical = 10  (1,5,10)
Impact = Critical =Threat x Vulnerability x Asset Value = 100*0.1*10=100
Likelihood = Medium = 0.5 (0.1,0.5,1)
Risk = Impact x Likelihood = 100 x 0.5 = 50 --> Medium 

Reference: https://blog.netwrix.com/2018/01/16/how-to-perform-it-risk-assessment/

Example Two : Qualitative TRA

Category	Security Control	Low	Moderate	High
Access Control	Administrator Multi Factor Authentication		x	x
Access Control	Centralized Authentication		x	x
Access Control	Machine Authentication		x	x
Access Control	Physical Security	x	x	x
Access Control	Role-based Authentication / Least Privilege		x	x
Access Control	Separation of duties		x	x
Access Control	User Multi Factor Authentication			x
Audit	Audit Data Review	x	x	x
Audit	Login Audit	x	x	x
Configuration Management	Configuration Change Control	x	x	x
Configuration Management	Notification of changes			x
Configuration Management	System Component Inventory	x	x	x
Contingency Planning	Contingency Plan	x	x	x
Contingency Planning	Disaster Recovery Site			x
Contingency Planning	Offsite Backup		x	x
Contingency Planning	Onsite Backup	x	x	x
Incident Response	Incident Response	x	x	x
Media Protection	Secure Delete		x	x
Risk Assessment	Penetration Testing			x
Risk Assessment	Vulnerability Management	x	x	x
System and Communication Protection	Data Leak Protection (DLP)		x	x
System and Communication Protection	DoS Protection			x
System and Communication Protection	Encryption at rest		x	x
System and Communication Protection	Encryption in transit	x	x	x
System and Communication Protection	Isolation in multi-tenant environment		x	x
System and Communication Protection	Network Segregation			x
System and Information Integrity	Antivirus/Antimalware	x	x	x
System and Information Integrity	File Integrity Monitoring		x	x
System and Information Integrity	Host IDS			x
System and Information Integrity	Network IDS		x	x
System and Information Integrity	Patch Management	x	x	x
System and Information Integrity	Priviledged Access Management			x
System and Information Integrity	System Hardening	x	x	x
System and Information Integrity	System Health Monitoring	x	x	x
Training	Awareness and Training	x	x	x

References

• 

• Canadian Centre for Cyber Security -Annex 3A - Security Control Catalogue (ITSG-33)