CAS-004 Security Engineering Practice Test 9 — 15 Questions

Question 1

An incident response team discovers that an attacker was able to forge a certificate for a legitimate domain. Which TWO mechanisms should the team implement to detect and prevent such misissuance in the future? (Select TWO.)

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Certificate Transparency (CT) logging and monitoring. Certificate Transparency (CT) logging and monitoring (D) is correct because CT requires CAs to submit every issued certificate to public, append-only logs, so the team can monitor these logs for unauthorized or forged certificates for their domains and detect misissuance quickly. Certificate pinning in client applications (E) is correct because it hardcodes or constrains the expected certificate/public key for a domain, so a forged certificate issued by a rogue or compromised CA will be rejected by the client, preventing its use even if it chains to a trusted root. CRLs (A) and OCSP stapling (C) only convey revocation status of certificates and cannot detect or prevent a newly forged certificate that has not yet been revoked, and EV certificates (B) merely assert a higher validation level without providing any detection or pinning mechanism against misissuance.

Answer

Certificate Revocation Lists (CRLs)

Answer

Implementing Extended Validation (EV) certificates

Answer

Online Certificate Status Protocol (OCSP) stapling

Question 2

A security analyst is reviewing cryptographic implementations for a new application. The application needs to support digital signatures that are quantum-resistant and provide high performance. Which TWO algorithms should the analyst consider? (Select TWO.)

Accepted Answer

XMSS (eXtended Merkle Signature Scheme). XMSS (eXtended Merkle Signature Scheme) (B) is correct because it is a hash-based, post-quantum digital signature scheme standardized in NIST SP 800-208, whose security relies only on hash function properties and is therefore resistant to Shor's algorithm attacks from quantum computers. CRYSTALS-Dilithium (E) is correct because it is a lattice-based post-quantum digital signature algorithm selected by NIST (FIPS 204) that offers strong quantum resistance with efficient signing and verification performance, making it well suited for high-performance applications. Ed25519 (A) is not correct because it is an elliptic-curve signature scheme (EdDSA over Curve25519) that is vulnerable to quantum attacks via Shor's algorithm. ECDSA P-384 (C) is not correct for the same reason: it is a classical elliptic-curve signature algorithm, not quantum-resistant. BLAKE3 (D) is not correct because it is a cryptographic hash function, not a digital signature algorithm, so it cannot fulfill the digital signature requirement.

Answer

Ed25519

Answer

ECDSA P-384

Answer

BLAKE3

Question 3

A company is implementing privileged access management (PAM) for its critical servers. Which THREE practices should be included to enhance security? (Select THREE.)

Accepted Answer

Record and monitor all privileged sessions. Option A is correct because recording and monitoring all privileged sessions provides an audit trail and enables real-time detection of malicious or anomalous activity by administrators, which is a core PAM control. Option B is correct because just-in-time (JIT) access provisioning grants elevated privileges only when needed and for a limited time, reducing the standing attack surface and the window for credential misuse. Option C is correct because break-glass accounts provide controlled emergency access when normal PAM workflows fail, and when properly vaulted, monitored, and alerted on, they preserve availability without creating unmanaged privileged access. Option D is not the best fit because MFA for all users is a general identity control, not a PAM-specific practice for critical server privileged access. Option E is not correct because periodic password rotation for service accounts is a legacy practice that can weaken security and is not a core PAM enhancement compared to session monitoring, JIT access, and break-glass procedures.

Answer

Enforce multi-factor authentication for all users

Answer

Require periodic password rotation for all service accounts

Question 4

A security architect is designing a secure boot chain for an IoT device. Which THREE components are essential to ensure the integrity of the firmware update process? (Select THREE.)

Accepted Answer

Firmware update files signed with a private key. Option A is correct because signing firmware update files with a private key lets the device verify authenticity and integrity using the corresponding public key, ensuring only authorized firmware is installed. Option D is correct because a secure OTA delivery mechanism such as TLS protects the update in transit against interception, tampering, and man-in-the-middle modification before it reaches the device. Option E is correct because a hardware root of trust, such as read-only memory storing the public key, provides an immutable anchor that validates the signature and boot chain, preventing attackers from substituting keys or firmware. Option B is not essential to integrity itself; rollback prevention is an anti-downgrade control that addresses version freshness rather than cryptographic integrity. Option C is also not essential, since encryption of firmware at rest protects confidentiality, not the integrity of the update process.

Answer

A mechanism to prevent firmware rollback to older versions

Answer

Encryption of firmware at rest on the device

Question 5

During a penetration test, an assessor successfully exploits a timing side-channel attack to extract an ECDSA private key from a secure enclave. Which TWO mitigations should the development team implement to prevent such attacks? (Select TWO.)

Accepted Answer

Implement constant-time cryptographic operations. Option A is correct because constant-time cryptographic operations ensure that execution time and memory access patterns do not depend on secret data, which directly eliminates the timing side-channel that leaked the ECDSA private key from the enclave. Option D is correct because ECDSA signing blinding (e.g., randomizing the nonce k and/or the private key d with a random value before the scalar multiplication) decorrelates the timing of the modular exponentiation/scalar multiplication from the actual secret, so an attacker cannot recover the key even if timing varies. Option B is not appropriate because adding random delays only obfuscates timing and is statistically defeatable by averaging many traces; it is not a sound cryptographic countermeasure. Option C does not belong because disabling debug interfaces addresses physical/JTAG-style access, not a timing side-channel observed through normal cryptographic execution. Option E does not belong because Ed25519 is also vulnerable to timing side-channels if implemented without constant-time code and blinding, so simply swapping algorithms does not fix the root cause.

Answer

Add random delays to cryptographic operations

Answer

Disable debug interfaces on the secure enclave

Answer

Replace ECDSA with Ed25519

Question 6

A security architect is designing a network for a financial services firm. The firm requires that all data in transit between its internal microservices be encrypted and mutually authenticated, but the services run in a containerized environment where static IP addresses are not available. Which of the following is the MOST appropriate solution to meet these requirements?

Accepted Answer

Deploy a service mesh with mutual TLS (mTLS) between sidecar proxies.. A service mesh with mutual TLS (mTLS) provides encryption and mutual authentication for service-to-service communication. It uses sidecar proxies to manage certificates and identity without relying on static IPs, which suits containerized environments. This directly meets the requirements for encrypted, mutually authenticated traffic in a dynamic infrastructure.

Answer

Implement IPsec tunnels between each container host.

Answer

Configure a VPN concentrator that all microservices connect to for encrypted communication.

Answer

Use TLS with server-side certificates only for each microservice.

Question 7

A security engineer is configuring a wireless network for a hospital. The network must support legacy medical devices that only support WPA2-Personal with pre-shared keys (PSK) and cannot be upgraded. The hospital also wants to prevent unauthorized devices from connecting and to detect rogue access points. Which of the following should the engineer implement to BEST meet these requirements?

Accepted Answer

WPA2-Personal with a strong, unique PSK and a wireless intrusion prevention system (WIPS).. WPA2-Personal with a strong PSK accommodates legacy devices that cannot use 802.1X. A WIPS monitors the airwaves for rogue access points and can detect and mitigate unauthorized devices. This combination meets the requirements without requiring device upgrades, balancing compatibility and security.

Answer

WPA2-Enterprise with 802.1X authentication and a RADIUS server.

Answer

Open network with a captive portal and MAC address filtering.

Answer

WPA3-Enterprise with 192-bit mode and a RADIUS server.

Question 8

A security analyst is reviewing the configuration of a web application firewall (WAF) protecting an e-commerce site. The analyst notices that the WAF is in detection-only mode. The site has been experiencing SQL injection attacks that are not being blocked. Which of the following actions should the analyst take to BEST protect the site while minimizing false positives?

Accepted Answer

Review the WAF logs, create custom rules to address the SQL injection patterns, and then switch to blocking mode.. Reviewing logs allows the analyst to understand the attack patterns and identify false positives. Creating custom rules tailors the WAF to the specific application, reducing false positives. Switching to blocking mode after tuning ensures that legitimate traffic is not disrupted while attacks are blocked.

Answer

Switch the WAF to blocking mode immediately.

Answer

Disable the WAF and rely on input validation in the application code.

Answer

Configure the WAF to block only requests from known malicious IP addresses.

Question 9

A security engineer is configuring a Linux web server that must accept TLS connections only from clients presenting a valid client certificate issued by the corporate internal CA. The engineer adds `SSLVerifyClient require` to the Apache configuration, restarts the service, and finds that all connections now fail with a handshake error. Which of the following is the MOST likely cause?

Accepted Answer

The `SSLCACertificateFile` directive pointing to the internal CA trust anchor is missing or incorrect.. Requiring client certificates forces the server to build and validate a chain from each client certificate to a trusted anchor. If the CA file that contains the internal root is absent or wrong, every validation fails and the handshake is torn down. Configuring the correct SSLCACertificateFile restores trust and allows valid clients to complete the handshake.

Answer

The server is missing an OCSP responder URL, so revocation checking fails and the handshake is rejected.

Answer

The client certificates were generated with ECDSA keys while the server is configured to accept only RSA client keys.

Answer

The `SSLProtocol` directive allows only TLSv1.3, which does not support client certificate authentication.

Question 10

A security engineer is designing the key-management lifecycle for a hardware security module (HSM) that will hold a root certificate authority signing key. The requirement is that the private key must never exist in plaintext outside the HSM, even during backup, and that restoration must be possible after a total device failure. Which approach BEST satisfies these requirements?

Accepted Answer

Configure the HSM to back up the key material using its secure backup mechanism to at least two geographically separate HSMs.. The only approach that keeps the private key inside a hardware-protected boundary while still allowing recovery is a vendor-supported secure backup or cloning mechanism between HSMs. Wrapping, plaintext export, and software encryption all allow the key to exist in a form that can be recovered outside certified hardware, which the scenario explicitly forbids.

Answer

Store the key on the HSM and replicate it to a spare HSM using the vendor's plaintext export option, then destroy the source.

Answer

Encrypt the private key with AES-256 in software and store the ciphertext on a hardened file server accessible only to administrators.

Answer

Export the private key wrapped under a key-encryption key, store the wrapped blob on encrypted network storage, and re-import it after failure.

Question 11

A security engineer is configuring a Linux bastion host that must expose SFTP to external partners while preventing interactive shell access for those same partner accounts. Partner keys are already deployed in each account's authorized_keys file. Which sshd_config directive combination BEST satisfies this requirement?

Accepted Answer

Set ForceCommand internal-sftp and ChrootDirectory /sftp/%u for the partner group in sshd_config.. Forcing the internal SFTP subsystem for matched sessions guarantees the connection can only perform file transfer, because the daemon never invokes the user's login shell. Combining that with a chroot directory confines each partner to a dedicated subtree and satisfies both the access and isolation goals with a single Match block. Authentication hardening alone does not change what a successfully authenticated session is allowed to do.

Answer

Set Subsystem sftp /usr/lib/openssh/sftp-server and PermitTunnel no in the global sshd_config.

Answer

Set PasswordAuthentication no and PubkeyAuthentication yes for the partner group in sshd_config.

Answer

Set PermitRootLogin no and AllowUsers partner1 partner2 in the global sshd_config.

Question 12

A security engineer is configuring a Linux server to enforce encrypted remote administration. The requirement is that after the initial key exchange, session keys must be rotated periodically to limit the impact of a compromised session key. Which OpenSSH configuration directive should the engineer use to achieve this?

Accepted Answer

Set RekeyLimit to 1G 1h in the sshd_config file.. The RekeyLimit directive in OpenSSH allows administrators to enforce periodic rekeying based on data volume, time, or both. By setting it to 1G 1h, the session key is refreshed after 1 gigabyte of data or one hour, whichever occurs first. This limits the amount of data encrypted under a single key, reducing the impact of a key compromise. Other directives control cipher selection, key exchange algorithms, or integrity algorithms but do not manage key rotation.

Answer

Set Ciphers to aes256-ctr in the sshd_config file.

Answer

Set MACs to hmac-sha2-512 in the sshd_config file.

Answer

Set KexAlgorithms to diffie-hellman-group-exchange-sha256 in the sshd_config file.

Question 13

A security engineer is implementing a secure software development lifecycle (SDLC) for a new application. The engineer needs to integrate security activities that help identify and mitigate vulnerabilities early in the development process. Which of the following activities should be included? (Choose two.)

Accepted Answer

Static application security testing (SAST) in the CI/CD pipeline.. Threat modeling during design and SAST in the CI/CD pipeline are both early-stage activities that help identify and mitigate vulnerabilities before deployment. Threat modeling addresses design flaws, while SAST catches coding errors. Together, they shift security left and reduce remediation costs.

Answer

Security awareness training for developers.

Answer

Penetration testing after production deployment.

Answer

Dynamic application security testing (DAST) during the design phase.

Question 14

A security architect must protect data at rest on a database server while allowing a backup application to read the raw encrypted files without ever holding the plaintext data key. The architect wants a design where a hardware security module (HSM) enforces key usage policy and keys never leave the module in plaintext. Which approach BEST satisfies these requirements?

Accepted Answer

Use envelope encryption where the data key is wrapped by a master key resident in the HSM, and decrypt the data key only inside the HSM for authorized operations.. Envelope encryption separates the bulk data key from a master key held inside the HSM. Backup processes can handle ciphertext without ever seeing the plaintext data key, because unwrapping occurs only within the HSM under its enforced policy. This design satisfies both the confidentiality requirement and the constraint that key material never leaves the hardware module.

Answer

Apply full-disk encryption with a passphrase-protected key and share the passphrase with the backup operators.

Answer

Encrypt the database with a key stored in a software keystore and grant the backup service read access to that keystore.

Answer

Store the data key in a TPM sealed to the database server's boot measurements and let the backup service request unsealing remotely.

Question 15

A security engineer is implementing a secure boot process for an embedded device. The engineer needs to ensure that only trusted firmware is executed and that the integrity of the boot chain is maintained. Which TWO of the following are essential components of a secure boot implementation? (Choose two.)

Accepted Answer

Digital signature verification of each boot stage. Secure boot requires an immutable root of trust to anchor trust and digital signature verification at each stage to ensure only trusted code executes. Encryption, secure enclaves, and TPMs can complement security but are not essential for the fundamental secure boot process.

Answer

Full disk encryption of the boot partition

Answer

Trusted Platform Module (TPM) for measured boot

Answer

Secure enclave for key storage