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Case Study: Risk Assessment of an Enterprise Call Accounting Solution

Part 2: Conducting the Security Risk Assessment

Why conduct a threat analysis?

"By retiring an aging 80’s in-house system and outsourcing to TACS we will move into the 21st Century in less than nine months; and get an easy to use service that’s available to all students and generates a revenue stream," said Steve Walz, Campton campus operations manager, “but we had security concerns about using an outsourced service.”

“We knew that TACS is an experienced call accounting solution provider but we were unsure that their software and operations team had adopted a best-practices approach to information security and we asked TACS to submit to an external assessment of their systems…” said Walz.

The six basic steps in a Practical Threat Analysis

A typical PTA - Practical Threat Analysis study focuses on protecting valuable assets, is sponsored by a senior manager, has 2-5 participants with relevant knowledge, is guided by an experienced security consultant, lasts 5 days and is facilitated by the PTA Professional Edition risk assessment software tool.

In a pre-kickoff planning meeting, the consultant works with the sponsor to set clearly defined goals and outcomes for the session. Since much of the work is done in small breakout groups, all stakeholders take an active part. The consultant guides the group through a fast-paced process to:

1-Identify assets
2-Identify vulnerabilities
3-Define countermeasures
4-Compose threat scenarios
5-Understand calculated risk
6-Optimize countermeasures

The PTA process is particularly effective because it is facilitated and accelerated with the accompanying PTA Professional Edition risk assessment tool that ensures that all the information is captured in a structured database and automates the economic risk what-if calculation process. Analysts and stakeholders don’t need to maintain unstructured Word or Excel documents and can quickly create new threat scenarios and countermeasures. All issues are captured and nothing is lost. Management can ask for and quickly receive any reports they want.

PTA kickoff

At the first day kickoff session, the functional and architectural descriptions of TACS’s system were presented to the Software Associates lead analyst, by Dympna O’Connell, TACS product manager. “We’re already documenting and revising our customer provisioning and configuration procedures”, said O’Connell. “We realize that these process steps are crucial to our customer's information security and we want to make sure there are no security holes and opportunities for data manipulation”.

Step 1 of the study – Identify Assets

In the first step of the study the group mapped the system’s major assets, their financial values and the losses that may be caused when assets are damaged. The following major system assets were identified:

The total value of all system assets was $2,210,000 - a detailed list of identified assets is part of the full threat-model database available for free download: The Threat Model of the Enterprise Call Accounting Solution. To view the detailed entities lists you should have the free PTA Risk Assessment Tool installed on your computer.

Step 2 – Identify Vulnerabilities

In order to identify vulnerabilities and flaws, Software Associates analysts studied the functional and architecture documents supplied by Ms. O’Connell. “Since TACS bases its architecture on Microsoft infrastructure, we used the PTA MS-Telecom entity library as a base line checklist for picking up system common vulnerabilities” said Yuval, Software Associates lead risk analyst. “More then 70% of the stuff was already there. We have just had to complement the picture by diving into the CDR collection equipment and by studying Campton specific business procedures with the help of Mr. Walz.

“Identifying the relevant vulnerabilities is an iterative process bundled with the understanding of the actual threats. All in all, we came up with 15 focused vulnerabilities relevant to the specific architecture, the specific telephony infrastructure and the ASP mode of operation” said Yuval.

Step 3 – Define Countermeasures

During this step the team defined the countermeasures relevant for mitigating the identified vulnerabilities. Some of the countermeasures were well known safeguards picked up from the predefined PTA entity library such as enforcing OS patches deployment and strong passwords policy. Others were more unique e.g. the development of mechanism for managing data collection buffer passwords in an encrypted repository.

“We worked directly with Ms. O’Connell and her developers on estimating countermeasures’ implementation costs needed by PTA for calculating countermeasures cost-effectiveness” said Yuval.

The lists of the 22 countermeasures that were defined and the identified vulnerabilities are included in the case study database available for free download: The Risk Assessment and Threat Analysis of the Enterprise Call Accounting Solution.

Step 4 – Build Threat Scenarios

“Building the threats is the peak of the process” said Software Associates founder and CTO Mr. Danny Lieberman, “this is the point where we use our experience to compose the threat scenarios, evaluate their feasibility and estimate the probability they’ll actually happen”.

“The flexibility of the PTA database driven model enables us ‘what-if’ experiments and the calculative capabilities gives us immediate feedback on the severity of threats” , said Yuval.

Step 5 - Understand the calculated Risk

After refining threat probabilities, the PTA software calculated the following bottom-line:

- The total yearly value of assets that might be damaged if threats materialize is $2.21M
- The risk level (the value of the financial losses that may be caused to the system due to the identified threats) is 249% of the total assets (~$5.5M). Although it is clear that the actual damage to the system’s assets cannot exceed their total value, the risk level does not express the actual damage. It reflects the amount of effort that has to be invested in order to mitigate the threats to the system, and since in this specific system several threats threaten the same assets, the risk level exceeds 100%.

The following bar chart presents the 5 most dangerous threats calculated and displayed by PTA (the value of risk is presented in real $):

Top Threats by Risk

Not surprising, it was found that the most dangerous threats are the ones that threaten the calls data either in the system’s database on the various collecting stages.

“The ranking of the threats reflects a typical heterogeneous software system. The ability to take into account non-standard threats specific to the analyzed system is one of the great strengths of PTA “ said Lieberman, “We weren’t limited to generic info security standards, such as ISO17799 and indeed you can see some interesting threats that indigenous to this particular system e.g. the CDR buffers vulnerabilities. Complex systems like this often have huge risks that are hidden in the cracks of generic standards…”

Step 6 – Optimize Countermeasures

It was clear that a level of 249% of risk is dangerous and that countermeasures should be applied to reduce the system’s risk before going into heavy-duty production operation.

“We asked Software Associates to show us how to reduce the risk to an acceptable level of 60% at lowest cost” said Steve Walz. “Since our budget was constrained, we considered canceling the whole info-sec project and taking our risks by doing nothing”.

“At that step we ran PTA ‘Optimized Risk Reduction Plan’ with the target risk level of ~ 50 %” said Yuval “and we received an optimized plan with the following countermeasures that should be applied:

1. Install content leakage prevention system
2. Install firewall
3. Enforce deployment of latest security patches for OS, database and Web server
4. Develop mechanism for secure managing of CDR buffers passwords
5. Use CDR buffers with secure transfer and login authentication protocols
6. Enforce security code review
7. Enforce data access via stored procedures with formal parameters content validation
8. Implement validation of input fields in web pages
9. Develop secured passwords and role-based mechanism for web users
10. Develop monitoring mechanism for back-end processing (system health)
11. Limit access of ASP employees and technicians to system resources
12. Enforce quality passwords policy for protecting each of the machines on the network
13. Use Windows integrated authentication policy
14. Database login accounts should be given the minimal rights that are necessary for their functionality

Implementing the recommended set of countermeasures reduces the system’s risk to 54.3% at a cost of 127,000 $. Only 14 countermeasures out of the 22 were selected - the proposed order of countermeasures also ensures a quickest reduction of risk per $ spent throughout the system modification process. The implementation of the following countermeasures was suspended to later stages in system life cycle:

- Create acceptable use policy for email and Internet access
- Install anti-DoS appliance
- Enforce deployment of latest security patches for OS, database and Web server
- Develop fraud detection mechanism
- Security officer should assure the personal integrity of employees
- Develop module for logging changes in data initiated by users
- Enforce employees' liability for disclosing private calls information
- Restrict display of phone numbers and sensitive information in detailed reports

“All-in-all, we were pleased with the speed and quality of results of the PTA methodology that Software Associates uses and with the fact that it created consensus among the stakeholders with effective use of senior manager time and above all got us the best risk reduction at the lowest cost…” summarized both Steve Walz of Campton College and Ms. O’Connell of TACS.

Appendix: Call Accounting Abbreviations and terminology

Download the Risk Assessment of the Enterprise Call Accounting Solution

The PTA threat analysis and risk assessment project of the Enterprise Call Accounting and Billing Solution is packed in a WinZip archive CallAccountingCaseStudy.zip. The archive contains the sample threat model database (a file with thm extension) and a few document files relevant to the project (doc and pdf). After downloading the archive, please extract the files to a dedicated folder according to your convenience and than invoke PTA* and open the thm database using the File / Open PTA Project dialog.

*Note: to view the sample threat model you should have the PTA Risk Assessment Tool installed on your computer.

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