SMB (Server Message Block) Hardening
The Server Message Block (SMB) is a network protocol that enables shared file access, printers, serial ports, and various communications between nodes on a network. This guide presents critical steps to harden and secure the SMB service.
Patch System Regularly​
Ensure to regularly apply patches and updates on your server. This action prevents exploits of known vulnerabilities in the SMB service.
sudo apt-get update && sudo apt-get upgrade # for Ubuntu
sudo yum update -y # for RH-based systems
This command updates the system packages including SMB.
Restrict Access​
Only allow essential and authorized systems to access the SMB ports. This restriction prevents unauthorized access.
sudo ufw enable # Enable firewall
sudo ufw deny from {unauthorized_IP_address} to any port 445
sudo ufw deny from {unauthorized_IP_address} to any port 135
This command blocks access to SMB ports.
Disable SMB 1​
SMB 1 is outdated and susceptible to numerous security vulnerabilities such as ransomware attacks. Disable SMB 1 to mitigate these risks.
echo "[global]" >> /etc/samba/smb.conf
echo "min protocol = SMB2" >> /etc/samba/smb.conf
This command disables SMB 1 on linux servers.
On Windows Server, follow these steps:
- Open Windows Features.
- Deselect SMB 1.0/CIFS File Sharing Support, and then click OK.
Enable SMB Signing​
SMB signing verifies the authenticity of SMB communications and prevents man-in-the-middle (MITM) attacks.
echo "server signing = mandatory" >> /etc/samba/smb.conf
echo "client signing = mandatory" >> /etc/samba/smb.conf
This command enables SMB signing on both the server and client sides.
Set Strong Passwords​
Use strong passwords for all user accounts. This action prevents unauthorized access.
sudo smbpasswd -a {username}
This command creates or updates the smb password of the user.
Limit SMB Permissions​
Limit permissions to what a user or a group of users need. This action prevents misuse of SMB.
chmod 770 {share_directory_path}
sudo chown {username}:{groupname} {share_directory_path}
This command sets directory permissions and ownership.
Enable SMB Encryption​
Use SMB encryption to protect against eavesdropping on untrusted networks.
echo "smb encrypt = mandatory" >> /etc/samba/smb.conf
This command enables SMB encryption.
Regular Auditing​
Perform regular audits of your SMB configuration and maintain logs for analysis.
testparm # Checks the Samba configuration file for internal correctness
This command validates smb configuration.