FTP and SFTP for file transfer in Computer Networks - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Difference in Security Between FTP and SFTP

Which statement best describes the main security difference between FTP and SFTP?

A SFTP encrypts both commands and data, while FTP sends data and passwords in plain text.

B FTP uses SSH for encryption, while SFTP uses SSL/TLS for encryption.

C FTP encrypts all data including passwords, while SFTP sends data in plain text.

D Both FTP and SFTP send data without any encryption by default.

💡 Hint

Think about which protocol uses SSH to secure the connection.

SFTP encrypts both commands and data using SSH, protecting passwords and files. FTP sends data and passwords in plain text, making it insecure.

📋 Factual

intermediate

Default Ports for FTP and SFTP

What are the default network ports used by FTP and SFTP respectively?

A FTP uses port 23, SFTP uses port 20.

B FTP uses port 21, SFTP uses port 22.

C FTP uses port 20, SFTP uses port 23.

D FTP uses port 22, SFTP uses port 21.

💡 Hint

Remember that SFTP runs over SSH which uses a specific port.

FTP typically uses port 21 for control commands, while SFTP uses port 22 because it runs over SSH.

🚀 Application

advanced

Choosing Between FTP and SFTP for Secure File Transfer

You need to transfer sensitive company files over the internet. Which protocol should you choose and why?

A Choose SFTP because it encrypts data and passwords, protecting sensitive information during transfer.

B Choose FTP because it is faster and does not encrypt data, so it uses less CPU.

C Choose FTP because it uses two ports which makes it more reliable for large files.

D Choose SFTP because it sends data in plain text, making it easier to debug transfer issues.

💡 Hint

Consider the importance of data privacy and protection during transfer.

SFTP encrypts all data and passwords, making it the secure choice for sensitive files. FTP does not encrypt data, risking exposure.

🔍 Analysis

advanced

Impact of Firewalls on FTP and SFTP Connections

Why can FTP connections be more difficult to manage through firewalls compared to SFTP?

A FTP uses a single port making it easy to block, while SFTP uses multiple ports.

B Both FTP and SFTP use the same ports, so firewalls treat them equally.

C SFTP requires opening many ports, while FTP only needs one port open.

D FTP uses multiple ports for control and data, requiring complex firewall rules; SFTP uses a single port.

💡 Hint

Think about how FTP opens separate connections for commands and data.

FTP uses port 21 for commands and opens additional ports for data transfer, complicating firewall configuration. SFTP uses a single port (22), simplifying firewall rules.

❓ Reasoning

expert

Evaluating Protocol Choice for Automated Backup Systems

An organization wants to automate backups to a remote server. The server supports both FTP and SFTP. Considering security, firewall complexity, and automation ease, which protocol is best and why?

A FTP is best because it uses multiple ports which allow parallel transfers improving speed for backups.

B SFTP is best because it sends data in plain text, making it easier to troubleshoot automated scripts.

C SFTP is best because it provides secure encrypted transfers and uses a single port, easing firewall setup and automation.

D FTP is best because it is widely supported and easier to automate without encryption overhead.

💡 Hint

Balance security needs with network and automation considerations.

SFTP offers encrypted transfers protecting backup data, uses a single port simplifying firewall rules, and is widely supported for automation, making it the best choice.

Practice

1. Which of the following statements correctly describes the main difference between FTP and SFTP?

easy

A. Neither FTP nor SFTP encrypt data during transfer.

B. SFTP encrypts data during transfer, while FTP does not.

C. Both FTP and SFTP encrypt data equally.

D. FTP encrypts data during transfer, while SFTP does not.

Solution

1. Step 1: Understand FTP security

   FTP is an older protocol that transfers files without encryption, making data vulnerable to interception.

2. Step 2: Understand SFTP security

   SFTP uses encryption to protect data during transfer, making it secure over untrusted networks.

3. Final Answer:

   SFTP encrypts data during transfer, while FTP does not. -> Option B

4. Quick Check:

   Encryption difference = SFTP encrypts, FTP does not [OK]

Hint: Remember: S in SFTP means Secure [OK]

Common Mistakes:

• Thinking FTP encrypts data
• Assuming both protocols are equally secure
• Confusing FTP with FTPS (which adds SSL)

2. Which of the following is the correct command to connect to a server using SFTP in a terminal?

easy

A. ftp [e-mail]

B. ssh [e-mail]

C. scp [e-mail]

D. sftp [e-mail]

Solution

1. Step 1: Identify SFTP command syntax

   The command to start an SFTP session is sftp [e-mail], which initiates a secure file transfer connection.

2. Step 2: Differentiate from other commands

   ftp is for FTP connections, ssh is for remote shell access, and scp copies files but is not an interactive file transfer session.

3. Final Answer:

   sftp [e-mail] -> Option D

4. Quick Check:

   SFTP command starts with 'sftp' [OK]

Hint: SFTP command always starts with 'sftp' [OK]

Common Mistakes:

• Using 'ftp' instead of 'sftp' for secure transfer
• Confusing SSH with SFTP command
• Using SCP which is not interactive

3. Consider this Python snippet using the paramiko library to upload a file via SFTP:

import paramiko
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect('example.com', username='user', password='pass')
sftp = client.open_sftp()
sftp.put('local.txt', 'remote.txt')
sftp.close()
client.close()

What will happen when this code runs successfully?

medium

A. The file 'local.txt' is uploaded securely to 'remote.txt' on the server.

B. The file 'remote.txt' is downloaded to 'local.txt' on the client.

C. An error occurs because paramiko does not support SFTP.

D. The connection is made but no file transfer happens.

Solution

1. Step 1: Understand paramiko SFTP usage

   The code connects to the server using SSH, then opens an SFTP session to transfer files securely.

2. Step 2: Analyze the sftp.put method

   sftp.put('local.txt', 'remote.txt') uploads the local file named 'local.txt' to the server as 'remote.txt'.

3. Final Answer:

   The file 'local.txt' is uploaded securely to 'remote.txt' on the server. -> Option A

4. Quick Check:

   sftp.put uploads local to remote [OK]

Hint: sftp.put uploads local file to server [OK]

Common Mistakes:

• Confusing upload with download (put vs get)
• Thinking paramiko does not support SFTP
• Assuming no file transfer happens without error

4. A user tries to connect to a server using SFTP but gets an error: Permission denied (publickey). What is the most likely cause?

medium

A. The SFTP command is not installed on the client machine.

B. The user typed the wrong server address.

C. The server requires a public key for authentication, but the user did not provide one.

D. The file transfer was interrupted by network issues.

Solution

1. Step 1: Interpret the error message

   Permission denied (publickey) means the server expects a public key for login but did not accept any provided or none was given.

2. Step 2: Rule out other causes

   Wrong server address or missing SFTP command would cause different errors. Network interruption would not cause a permission denied error.

3. Final Answer:

   The server requires a public key for authentication, but the user did not provide one. -> Option C

4. Quick Check:

   Public key error means missing or wrong key [OK]

Hint: Permission denied (publickey) means missing SSH key [OK]

Common Mistakes:

• Assuming network issues cause permission denied
• Thinking the command is missing on client
• Confusing server address errors with authentication errors

5. You need to securely transfer multiple files from your local machine to a remote server over an untrusted network. Which approach is best to ensure security and efficiency?

hard

A. Use SFTP to transfer files directly with encryption.

B. Use FTP with a VPN connection to encrypt the data.

C. Use FTP without encryption because it's faster.

D. Use HTTP to upload files through a web browser.

Solution

1. Step 1: Evaluate security needs

   Since the network is untrusted, encryption is necessary to protect data during transfer.

2. Step 2: Compare transfer methods

   SFTP provides built-in encryption and secure authentication, making it ideal for secure file transfer. FTP alone is not secure, even with VPN it adds complexity. HTTP is not designed for secure file transfer.

3. Final Answer:

   Use SFTP to transfer files directly with encryption. -> Option A

4. Quick Check:

   SFTP = secure and efficient file transfer [OK]

Hint: Choose SFTP for secure file transfer over untrusted networks [OK]

Common Mistakes:

• Relying on FTP without encryption
• Assuming VPN always solves FTP security
• Using HTTP which is not meant for file transfer