Which of the following is an encryption tool?

• A. Stunnel
• B. VeraCrypt
• C. Nessus
• D. Open SSH

Answer: (A)

Encryption tools protect data by turning it into ciphertext, typically to secure communications or stored data. Stunnel does this by acting as a TLS/SSL wrapper that secures existing TCP connections. It doesn’t reinvent how the data is used; instead, it encrypts the traffic between endpoints by tunneling it through TLS, so any non-encrypted protocol can be secured transparently. That focused role—adding encryption to other services’ communications—fits the idea of an encryption tool for data in transit.

By comparison, VeraCrypt is designed for disk or container encryption (data at rest), Nessus is a vulnerability scanner, and OpenSSH provides secure remote access using encryption as part of its protocol but isn’t just an encryption tool in the same sense as a TLS wrapper.