Everything About SMB Ports Firewall You Should Know

The SMB protocol allows for inter-process communication. This protocol enables services and applications on networked systems to interact with each other.

In other words, one can say that SMB is one of the common language systems used to talk to one another. Here is everything about SMB Ports Firewall for you.

How Does this SMB Protocol Function?

In earlier Windows versions, the SMB used to run on top NetBIOS network architecture. Microsoft modified SMB in Windows 2000 for operating on some top TCPs, where it employed a devoted IP port. In recent Windows versions, it continues to employ the same port.

Microsoft has even made advancements to SMBs for better security and performance. With SMB2, it has reduced the entire verbosity of the protocol.

On the other hand, SMB3 comprises enhancements and performance for virtualized surroundings and support for end-to-end and strong encryption.

SMB Protocol Dialects

Computer programmers have produced diverse SMB dialects like other languages for diverse purposes. For instance, CIFS (Common Internet File System) is the particular SMB implementation that allows file sharing.

Most people consider CIFS as a different protocol instead of SMB, where in fact, they both use a similar basic architecture.

Some of the significant SMB implementations comprise:

  • Samba: It refers to an open-source implementation from Microsoft Active Directory. This implementation enables non-Windows systems to interact with a Windows system.
  • CIFS: It is a typical file-sharing protocol that Windows servers use. CIFS is also compatible with NAS devices.
  • MoSMB: This implementation is a proprietary SMB introduced by Ryussi Technologies.
  • NQ: It is another portable SMB implementation for sharing files. Visuality Systems developed this SMB implementation.
  • Likewise: It is an identity-aware, multi-protocol network protocol for sharing files. EMC purchased this protocol in 2012.
  • Tuxera SMB: It is another proprietary SMB implementation which runs in either user-space or kernel.

Now, it is time to know about SMB ports firewall and other things about SMB ports. Let’s start by talking about SMB ports 445 and 139.

Also, click here to read more about the Mikrotik Firewall rules.

What Do You Mean by SMB Ports 445 and 139?

SMB is a network protocol for sharing files. It requires SMB network ports on a server or computer to allow communication with other systems. For this, it uses SMB ports, either port 445 or 139.

  • Port 139: Originally, SMB used to run on top NetBIOS with port 139. Here, NetBIOS refers to an older transport layer that enables Windows systems to interact with one another, sharing a similar network.
  • Port 445: The later SMB versions after Windows 2000 started using IP port 445 on top of TCK stacks. With TCP, it enables SMBs to operate over the internet.

IP Port 139 is technically called ‘NBT over IP,’ while IP Port 445 is referred to as ‘SMB over IP’. Here, SMB refers to ‘Server Message Blocks.’ In modern language, SMB is also called the ‘Common Internet File System.’

It functions as the application-layered network protocol, mainly used for providing shared access to printers, files, serial ports, or other kinds of communications among nodes on the network.

Most SMB usage involved systems running on Microsoft Windows. Here, this network came to know as ‘Microsoft Windows Network’ before the consequent Active Directory’s introduction. It runs on top network layers of the Session in manifold ways.

For example, SMB runs directly over IP/TCP on Windows without the requirement of NetBIOS over IP/TCP. In that case, you will use IP port 445. While on other computers, you will come across applications and services using IP port 139. The SMB ports firewall runs with NetBIOS over IP/TCP.

NetBIOS refers to Network Basic Input Output System. This software protocol enables desktops, applications, and PCs on a LAN (Local Area Network) to interact with one another or network hardware.

It even allows them to transmit the data over the network. For instance, software applications, which run on NetBIOS networks, identify and locate one another through the NetBIOS usernames.

NetBIOS names go up to 16 characters and are generally distinct from the system name. When a client sends out a command to call the other one (the server), two applications begin a NetBIOS conference over TCP port 139.

Malicious attackers admit that IP port 445 is susceptible and features various insecurities. An example of the misuse of SMB ports is the comparatively silent NetBIOS worms’ appearance.

Slowly, these worms scan the internet in a well-mannered way while the port uses tools like PsExec to transfer themselves into a fresh victim system.

After this, the worms redouble the scanning efforts. In this unfamiliar way, the enormous ‘Bot Armies,’ having thousands and thousands of NetBIOS worms conceded machines, get assembled and reside on the internet.

Why Do Users Need SMB Port 139?

NetBIOS over the internet or on the WAV is a high-security risk. Through NetBIOS, all kinds of information, like your workgroup, system, and domain names, along with the account details, can be accessed.

Thus, it is important to preserve the NetBIOS on the preferred network and also make sure it does not leave your network.

SMB ports firewall always restricts this port in the first place as a safety measure if users have opened it. This port 139 is employed for File and Printer Sharing.

However, it appears to be the most dangerous port you will find on the internet. The port leaves the user’s hard disk exposed to cybercriminals.

Once a cybercriminal has found an active IP port 139 on any device, he runs NBSTAT, which is a diagnostic program for NetBIOS over IP/TCP.

This application is designed primarily to help troubleshoot the name resolution issues associated with NetBIOS. It makes a significant step in an outbreak called Footprinting.

With the NBSTAT command, attackers can access all or some of the critical data associated with:

  1. System name
  2. IP addresses
  3. A record of local NetBIOS usernames
  4. A name list fixed by WINS
  5. The session table’s contents, along with the IP addresses’ destination

Along with these details, the cybercriminal takes all the significant information regarding service, OS, and chief applications that run on the computer.

Apart from these, the attacker monitors private IP addresses that the WAN/LAN, which security engineers try hard to keep behind NAT. Furthermore, user IDs are even included in the lists offered by running NBSTAT.

It makes it easier for attackers to enjoy remote access to the content of the drives or directories of the hard disk. After this, they upload and run their preferred programs silently through some freeware programs without the knowledge of the system owner.

Users who use a multi-homed system can disable NetBIOS on all network cards or under the IP/TCP properties, Dial-Up Connection, which is not a local network unit.

Also, everything about AlgoSec Firewall Analyzer.

How Can Users Deal with IP Port 445?

Keeping in view the above-mentioned perils, it is best that users do not expose Port 445 to the internet. However, Port 445 is profoundly entrenched in Windows, just like Port 135. Thus, it becomes difficult to close it safely.

Having said that, it is quite possible to close it; however, various other dependent tools or services like Dynamic Host Configuration Protocol (DHCP), which is often employed for obtaining IP addresses from DHCP servers automatically, are used by most ISPs and corporations will stop operating.

By the way, click here for the full Proxy vs. Firewall comparison.

Different Ways to Keep SMB Ports Secure

Keeping network SMB ports open to enable applications to operate is a security risk. So, users might be thinking about how they can keep their networks protected and maintain application operations.

Here, we have come up with some options to help you secure the two most important and popular SMB ports firewalls.

  1. Download a VPN for protecting and encrypting network traffic.
  2. Allow endpoint protection or SMB ports firewall for protecting the ports from cyber criminals. Many solutions comprise a blacklist for preventing the connection from familiar IP address attackers.
  3. Implement a VLAN for isolating inner network traffic.
  4. Employ MAC address filters to keep unknown systems from accessing the network. However, it requires substantial management to keep the list always maintained.

Apart from these particular network protections stated above, users can also implement a data-centric security strategy for protecting their most significant resource, which is the data stored on the SMB file shares.

It is a pretty monumental task to understand who can access the sensitive data over the SMB shares. Varonis tracks the data and access rights.

It even discovers the sensitive data present on the SMB shares. It is essential to monitor the data to detect progressive attacks. Plus, it is important to protect the data against breaches.

Varonis shows you where the data is insecure on the SMB ports. It even monitors those SMB shares for irregular access and impending cyberattacks.

Before you go for SMB ports firewall, it is best to check out a demo to see how Varonis tracks CIFS on EMC, NetApp, Samba shares, and Windows to keep the data safe.



Ten years of experience in information and computer technology. Passionate about electronic devices, smartphones, computers, and modern technology.