FTP/SFTP

FTP and SFTP are protocols for transferring files over networks.

FTP (File Transfer Protocol)

Basics

Older protocol
No encryption
Sends password in plaintext
Two connections: control and data
Ports: 20 (data), 21 (control)

Why Not FTP?

Insecure (passwords visible)
Complex firewall requirements
No data integrity checking
Deprecated in favor of SFTP

SFTP (SSH File Transfer Protocol)

Advantages

Encrypted (uses SSH)
Single connection
Better firewall compatibility
Port 22 (same as SSH)
More secure
Recommended standard

Using SFTP

Command Line

# Connect to SFTP server
sftp user@example.com

# Connect on different port
sftp -P 2222 user@example.com

# Upload file
put local_file remote_path
put /tmp/file.txt /home/user/

# Download file
get remote_file local_path
get /home/user/file.txt /tmp/

# List files
ls
ls -la

# Change directory
cd /home/user

# Create directory
mkdir new_folder

# Delete file
rm file.txt

# Exit
bye

Batch Transfer

# Upload multiple files
sftp user@example.com << EOF
put file1.txt
put file2.txt
bye
EOF

# Using scp (simpler)
scp file.txt user@example.com:/home/user/
scp -r directory/ user@example.com:/home/user/
scp user@example.com:/home/user/file.txt /tmp/

SFTP Server Setup

Using SSH

# SFTP is built into SSH
# Install SSH
sudo apt install openssh-server

# Enable SFTP subsystem
# /etc/ssh/sshd_config
Subsystem sftp /usr/lib/openssh/sftp-server

# Restart SSH
sudo systemctl restart ssh

# Create SFTP user
sudo useradd -m -s /usr/sbin/nologin sftp_user
sudo passwd sftp_user

Restrict User to SFTP Only

# /etc/ssh/sshd_config
Match User sftp_user
    ChrootDirectory /home/sftp_user
    ForceCommand internal-sftp
    PermitTTY no
    X11Forwarding no
    PasswordAuthentication yes

GUI Tools

FileZilla

# Install
sudo apt install filezilla

# Run
filezilla

Configuration:

Host: sftp://example.com
Port: 22
Username: user
Password: pass
Connect

WinSCP (Windows)

Connect with SFTP protocol
Host: example.com
Port: 22
Drag and drop files

Common Commands

# Check if SFTP is working
sftp -T user@example.com

# Verbose output
sftp -v user@example.com

# Use specific key
sftp -i /path/to/key user@example.com

# Transfer rate
sftp -l 1000 user@example.com

Monitoring

# Check SFTP logs
sudo tail -f /var/log/auth.log | grep sftp

# Monitor active connections
ss -tuln | grep 22

Security Best Practices

Use SFTP, not FTP
Disable FTP entirely
Use SSH keys instead of passwords
Restrict SFTP to specific directories
Monitor SFTP access
Keep SSH updated
Use strong passwords
Implement rate limiting
Use VPN for sensitive transfers
Verify checksums after transfer

FTP/SFTP

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