CSSLP Secure Software Concepts — 20 Questions

Question 1

You are applying the Bell-LaPadula model to a secure software system. A user with 'Secret' clearance attempts to write data to a 'Top Secret' file. Based on the *-property, what is the outcome?

Accepted Answer

The write is denied because the *-property prohibits writing to a higher security level.. The *-property (star-property) of Bell-LaPadula prevents 'write-down', meaning a subject cannot write to a lower level, but also enforces no-read-up/no-write-down rules.

Answer

The write is permitted.

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The write is denied due to the no-write-down rule.

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The system allows the write only if encryption is used.

Question 2

A developer is configuring a web application to use the principle of least privilege. Which action best aligns with this philosophy?

Accepted Answer

Using a dedicated service account with granular permissions for database access.. Least privilege requires granting only the minimum necessary permissions for a task.

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Granting the application access to all system environment variables.

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Enabling 'Everyone' write access to application configuration files.

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Running the application process as 'root' or 'administrator'.

Question 3

A security auditor reviews your code and flags that you are using 'hardcoded cryptographic keys' in the source repository. Which security concept is being violated?

Accepted Answer

Confidentiality. Hardcoded keys violate confidentiality because the keys are exposed to anyone with access to the source code.

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Availability

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Non-repudiation

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Integrity

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Accounting

Question 4

In an OAuth 2.0 flow, you are using the 'Authorization Code' grant type. You notice an attacker is attempting to intercept the code. Which security concept is being utilized by requiring the client_secret during the token exchange?

Accepted Answer

Authentication. The client_secret provides authentication of the client to the authorization server, ensuring only the intended client can exchange the code.

Answer

Availability

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Non-repudiation

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Confidentiality

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Integrity

Question 5

When implementing the Biba Integrity Model, which operation is restricted for a subject to maintain the integrity of a higher-level object?

Accepted Answer

Read-down. Biba is the inverse of Bell-LaPadula, focusing on integrity. It prevents 'read-down' to ensure a process doesn't ingest corrupted data from a lower level.

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Read-up

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Write-up

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Execute-down

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Append-down

Question 6

A developer is performing a threat modeling exercise using STRIDE. What does the 'S' in STRIDE represent?

Accepted Answer

Spoofing. STRIDE stands for Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, and Elevation of privilege.

Answer

Software integrity

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Service availability

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System hardening

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Secure architecture

Question 7

Your application uses digital signatures to confirm the sender of a message. Which security goal is primarily achieved?

Accepted Answer

Non-repudiation. Digital signatures are the standard mechanism for proving authenticity and non-repudiation.

Answer

Authorization

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Encryption

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Availability

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Confidentiality

Question 8

A software architect is designing a system where data must remain accessible even if the primary database server fails. They implement a synchronous database replication strategy. Which core security concept is being prioritized?

Accepted Answer

Availability. Availability is prioritized by ensuring data access despite server failure through replication.

Answer

Non-repudiation

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Integrity

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Confidentiality

Question 9

Which of the following is an example of defense-in-depth in a web application architecture?

Accepted Answer

Implementing input validation, parameterized queries, and a Web Application Firewall (WAF).. Defense-in-depth uses multiple layers of security so that if one fails, others compensate.

Answer

Disabling all firewall rules for testing purposes.

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Storing all application data in a single encrypted volume.

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Removing all logs to prevent unauthorized access to audit trails.

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Using a single strong password for all database accounts.

Question 10

What is the primary goal of the 'Principle of Least Privilege' (PoLP)?

Accepted Answer

To restrict access to the minimum necessary for a task.. PoLP ensures that entities are granted only the minimum level of access required to perform their functions.

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To simplify administrative tasks by giving everyone full access.

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To ensure that security controls are invisible to users.

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To provide all users with the same set of permissions.

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To automatically grant permissions based on time of day.

Question 11

You are designing a system to comply with 'Fail-Safe Defaults'. Which configuration best reflects this?

Accepted Answer

If the authorization check fails, explicitly deny the request.. Fail-safe defaults mean that if an error or crash occurs, the system defaults to the most secure state (e.g., access denied).

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If the authentication service is down, allow access to all users.

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If the firewall fails, allow all traffic to pass through.

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Default all new user accounts to 'Administrator' role.

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If the load balancer times out, bypass the application logic.

Question 12

A security team implements a 'Separation of Duties' policy in the CI/CD pipeline. Which implementation is correct?

Accepted Answer

One developer commits code, and a separate user with deployment permissions triggers the release.. Separation of Duties prevents one person from having enough access to execute a malicious change without oversight.

Answer

The same developer writes, reviews, and deploys the code.

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The QA team is allowed to modify production database records.

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The build server automatically deploys code without human verification.

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All developers have access to the production environment credentials.

Question 13

When designing secure software, why is 'Economy of Mechanism' important?

Accepted Answer

To minimize the attack surface by keeping the design simple.. Economy of mechanism suggests that designs should be as simple and small as possible to minimize the attack surface and make security easier to verify.

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To lower the cost of hardware infrastructure.

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To increase the lines of code for better functionality.

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To ensure that the software is faster at runtime.

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To enable easier debugging for developers.

Question 14

Which concept describes the ability of a system to provide services to authorized users even during a heavy load or denial of service attack?

Accepted Answer

Availability. Availability specifically refers to the system's ability to remain operational and accessible.

Answer

Non-repudiation

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Integrity

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Authentication

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Confidentiality

Question 15

You are using the 'Complete Mediation' principle in your system's access control design. What does this require?

Accepted Answer

Checking authorization for every access request.. Complete mediation requires that every access request to every object must be checked for authorization, with no caching or bypassing allowed.

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Granting permanent access to all authenticated users.

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Checking authorization only at login.

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Relying on the user to request access when needed.

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Caching permissions to reduce latency.

Question 16

An application utilizes the Clark-Wilson integrity model. Which mechanism does it use to ensure that subjects only perform authorized operations on objects?

Accepted Answer

Transformation Procedures (TPs). Clark-Wilson uses Transformation Procedures (TPs) to move system state from one consistent state to another, strictly controlling access.

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Role-Based Access Control (RBAC)

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Attribute-Based Access Control (ABAC)

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Discretionary Access Control (DAC)

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Security Labels

Question 17

You are implementing 'Psychological Acceptability' in a new multi-factor authentication system. Which design choice is most appropriate?

Accepted Answer

Using a user-friendly mobile app push notification for authentication.. Psychological acceptability ensures that security measures are easy for users to understand and use, so they don't circumvent them.

Answer

Providing zero feedback to users during the login process.

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Requiring a 64-character password changed every 24 hours.

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Disabling the ability for users to reset their own passwords.

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Forcing users to solve a complex CAPTCHA at every login attempt.

Question 18

When implementing a 'Zero Trust' architecture in software design, which THREE principles are fundamental?

Accepted Answer

Assume breach. Zero trust assumes no implicit trust and requires constant verification.

Answer

Trust but verify

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Trust all internal network traffic

Question 19

Which TWO of the following are examples of how software can maintain 'Integrity'?

Accepted Answer

Using cryptographic hash functions (e.g., SHA-256) to verify file contents.. Integrity is maintained through mechanisms that ensure data is not tampered with.

Answer

Encrypting data at rest using AES.

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Ensuring the server is always online.

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Forcing users to change passwords regularly.

Question 20

Which TWO of the following are recognized components of the 'Confidentiality, Integrity, and Availability' (CIA) triad?

Accepted Answer

Integrity. The CIA triad consists of Confidentiality, Integrity, and Availability.

Answer

Non-repudiation

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Accounting

Answer

Authentication