CISO AppSec Guide: Metrics For Managing Risks & Application Security Investments

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Part IV: Metrics For Managing Risks & Application Security Investments


The aim of this part of the guide is to help CISO to manage the several aspects of the application security program specifically risk and compliance as well as application security resources such as processes, people and tools. One of the goals of the application security metrics is to measure application security risks as well as compliance with application security requirements mandated by information security standards. Among critical application security processes that the CISO need to report of and manage are application vulnerability management. It is often CISO responsibility for example to report the status of the application security activities to senior management such as the status of application security testing and software security activities in the SDLC. From the risk management perspective it is important that the application security metrics allow to reports on the technical risks such as the un-mitigated vulnerabilities for the applications that are developed and managed by the organization. Another important aspect of the application security metrics is to measure coverage such as the percentage of the application’s portfolio regularly assessed in application security verification program, the percentage of internal apps vs. external apps covered, the inherent risk of these apps and the type of security assessments performed on these applications and when in the SDLC are performed. This type of metrics helps the CISO in reporting on application security process compliance and application security risks to the head of the information security as well as to the application business owners.

Since one of the CISOs responsibilities is to manage both information security and applications security risks and to make decisions on how to mitigate them, it is important for this metrics to be able to measure these risks in terms of vulnerability exposure to the organization’s assets that include application’s data and functions.

Application Security Process Metrics

Metrics and Measurements Goals

The goal of the application security process metrics is to determine how good are the organizations application security processes in meeting the security requirements set forth by application security policies and technical standards. For example an application vulnerability process might include requirements to execute vulnerability assessments on internet facing applications every six or twelve months depending on the inherent risk rating of the application. Another vulnerability process requirement would be to execute security in the SDLC type of processes such as architecture risk analysis/threat modeling, static source code analysis/secure code reviews and risk based security testing on applications that store customer’s confidential information and whose business functionality is a critical service to customers.

From the perspective of process coverage, one of the goals of this metrics might be to report on the coverage of application security process such as to measure how applications fall in scope for application security assessments to identify potential vulnerability assessment gaps based upon application type and the application security requirements. This type of metrics helps the CISO to provide visibility on process coverage as well as the status of the operational execution of the application security programs. For example the metrics might show (e.g. in red status) that some of the application security processes in the SDLC such as secure code reviews are not executed in some of the high risk rated applications and flag this as an out of compliance issue with the security testing requirements. This type of metrics allow the CISO to prioritize resources by allocating them on where is most needed to comply with the standard process requirements.

Another important measurement for application security testing is to measure the time of when the application security processes are scheduled and executed to identify potential delays in the scheduling and execution of application security processes such as secure code review/static source code analysis as well as ethical hacking/application pen testing.

Application Security Risk Metrics

Vulnerability Risk Management Metrics

One of CISO responsibilities is to manage application security risks. From technical risk perspective, application security risks might be due to vulnerabilities in the applications that might expose the application assets such as the data and the application critical functions to potential attacks seeking to compromise the data and/or the critical functions that the application provides. Typically, technical risk management consists on mitigate the risks posed by vulnerabilities by applying fixes and countermeasures. The mitigation of the risk of these vulnerabilities is typically prioritized based upon the qualitative measurement of risks. For example, for each application that is developed and managed by the organization that would be a certain number of vulnerabilities identified at high, medium and low risk severity. The higher the number of high and medium risk vulnerabilities the higher is the risk to the application. The higher the value of the data assets protected by the application and the criticality of the functions supported, the higher the impact of these vulnerabilities on the application assets.

One important emphasis that is given in the vulnerability metrics is the determination of the number of vulnerabilities that are still not fixed. A given number of application vulnerabilities might still be “open” that is not yet fixed in production environment: these represent a risk to the organization and require the CISO to prioritize the risk mitigating action such as “closing” the vulnerability within the compliance timeframes that is deemed acceptable by the application vulnerability management standards.

Security Incident Metrics

Another CISO important metrics for the managing of information security risks is the reporting of security incidents for applications that are developed and/or managed by the organization. The CISO might gather this data from reported from SIRT (Security Incident Response Team Incidents) that affect a given application such as breaches of data as results of an exploit of a vulnerability. The correlation of the security incidents reported for a given application with the vulnerabilities reported by security testing allows the CISO to prioritize the risk mitigation effort on mitigating vulnerabilities that might cause the most impact to the organization. Obviously, waiting for a security incident to occur to decide which vulnerabilities to mitigate is symptomatic of a reactive rather than proactive approach toward risk management.

Threat Intelligence Reporting and Attack Monitoring Metrics

Risk proactive organizations do not wait for security incidents to occur but rather learn from information about attacks and threat intelligence and use that information to take proactive risk mitigation measures such as to develop and implement countermeasures yet mitigating all high risk known vulnerabilities that might be potentially exploited in an incident to cause the most impact to the organization. The CISO can use threat intelligence reports as well as metrics from monitored application layer security events such as from SIEM (Security Incident Event Management) systems to assess the level of risk. Unfortunately today, most of security incidents are discovered and reported only after months from the initial intrusion or data compromise. A security metrics that is actionable toward preventing risks of attacks is of critical importance for CISO since it might allow deciding which applications to put under alert and monitoring and to act quickly in the case of an attack. For example a threat alert of a possible distributed denial of service against online banking applications might allow the CISO to put the organization on alert and prepare to roll out countermeasures to prevent outage. A reported threat of malware targeting online banking applications to steal user credentials and conduct un-authorized financial transactions for example allows the CISO to issue monitoring alerts for the online banking application secure incident event monitoring management team.

Security in SDLC Management Metrics

Metrics for Risk Mitigation Decisions

Once vulnerabilities are identified the next step is to decide which should be fixed and when and how should be fixed. The first question can be answered by the vulnerability assessment process compliance requirements that might require for example of high risk type of vulnerabilities to be remediated in shorter time frames than medium and low risk type of vulnerabilities. The requirement might also vary depending on the type of application, being for example a totally newly developed application versus a new release of an existing application. Since new applications were not security tested before, they represent higher risks than existing applications and therefore this might require that high risk vulnerabilities to be mitigated prior to release the application in the production. Once the issues are identified and prioritized for mitigation based upon the risk severity of the vulnerability, the next step is to determine how to fix the vulnerability. This depends on factors such as the type of the vulnerability such as the security controls/measures that are affected by the vulnerability and where the vulnerability is most likely being introduced. This type of metrics allows the CISO to point to the root causes of vulnerabilities and present the case for remediation to the application development teams.

Metrics for Vulnerability Root Causes Identification

When the vulnerability metrics is reported as a trend, it allows the CISO to assess improvements. For example, in the case the same type of security issues are measures over time for the same type of application, it is possible for the CISO to point to potential root causes. For example, with trend vulnerability metrics and categorization of the type of vulnerabilities, it is possible for the CISO to make the case of investing in certain type of security activities such as process improvements, adoption of testing tools as well as training and awareness. For example, the metrics showed in figure 1 shows positive trends of certain type of vulnerabilities by comparing two quarterly releases of the same applications. Application security improvements measures as a reduced number of vulnerabilities identified from one quarterly release to another is observed for most vulnerability types except for authentication and user/session management issues.

VA Metrics.jpg

The CISO might use this metrics to discuss with CIOs and development directors on whether the organization is getting better or worst over time in releasing more secure application software and to direct the application security resources (e.g. process, people and tools) where is most needed for reducing risks. With the metrics shown in Figure 1 for example, assuming the application changes introduced between releases do not differ much in term of type and complexity of the changes introduced as well as the number and the type of software developers in the development team and the tools used, a case can be made on focusing on the type of vulnerabilities that the organization is having trouble fixing such as better design and implementation of authentication and user/session management controls. The CISO might then coordinate with the CIO and the development directors to schedule a targeted training on this type of vulnerabilities, document development guides for authentication and session management and adopt specific security test cases. Ultimately this coordinated effort will empower software developers in designing, implementing and testing more secure authentication and session management controls and show these as improvements in the vulnerability metrics.

Metrics for Software Security Investments

Another important aspect of the S-SDLC security metrics is to decide where in the SDLC to invest in security testing and remediation. To know this, it is important to measure in which phase of the SDLC the most of vulnerabilities (higher percentage of issues) originate, when these vulnerabilities are tested and how much cost to the organization to fix them in each phase of the SDLC. A sample metrics that measure this is shown in figure 2 based upon a case study on the costs of testing and managing software bugs (Ref Capers Jones Study).

Issue SDLC metrics.jpg

A similar type of security defect management metrics can be used by the CISOs for managing security issues effectively by reducing overall security costs. Assuming the CISO has rolled out a security in the SDLC process and has budget allocated for investment in security in the SDLC activities such as secure coding training and secure code review process and static code analysis tools, this metrics allows the CISO to make that case for investing in testing and fixing security issues in the early phases of the SDLC. This is based upon the following measurements from this case study: 1) most of the vulnerabilities are introduced by software developers during coding, 2) the majority of these vulnerabilities are tested during field tests prior to production and 3) testing and fixing vulnerabilities late in the SDLC is the most inefficient way to do it since is approx. ten times more expensive to fix issues during pre-production tests than during unit tests. CISOs can use vulnerability case studies like these or use their own metrics to make the case for investing in secure software development activities since these will save the organization time and money.