Smb port number
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If you use a Windows 10 or later system, the fixes are already built in. The March 2017 update from Microsoft can assist in patching the server message block vulnerabilities. However, NetBIOS services historically required UDP for name resolution and datagram services.
Does SMB Use Both Ports 445 and 139?
Most modern environments use only port 445, but older systems may still use both ports 445 and 139.
SMB still uses port 445.
This proved to be problematic as CIFS was a notoriously chatty protocol that could ruin network performance due to latency and numerous acknowledgments. SMB enables network functions like file, print and device sharing, among others.
SMB Ports Explained
SMB ports are used for file sharing, enabling programs and services on networked computers to communicate with each other.
What Are SMB Ports?
The server message block (SMB) protocol provides “client-server communication,” which allows programs and services on networked computers to communicate with one another. The transport code scans for systems vulnerable to the EternalBlue exploit and then installs DoublePulsar, a backdoor tool, and executes a copy of itself.
An infected computer will search its Windows network for devices accepting traffic on TCP ports 135-139 or 445, indicating the system is configured to run SMB.
It will then initiate an SMBv1 connection to the device and use buffer overflow to take control of the system and install the ransomware component of the attack.
This means WannaCry can spread automatically without victim participation.
The good news is that the Windows has since released a security update to Windows XP, Windows Server 2003, Windows 8, Windows Vista, Windows 7, Windows 8.1, Windows 10, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012 and Windows Server 2016 to prevent this exploit.
How to Keep Ports 139 and 445 Secure
Here are some other ways you can keep ports 139 and 445 secure from hackers.
Avoid Exposing SMB Ports
Ports 135-139 and 445 are not safe to publicly expose and have not been for a decade.
Patch Everything
Keep your systems up-to-date to avoid exploits of known vulnerabilities and cyberattacks such as NetBIOS name service (NBNS) spoofing and Main-in-the-Middle (MITM) attacks.
No Single Point of Failure
Whether it's ransomware, malware, hardware failure, database error, or something else.
While SMB ports have relied on different protocols through the years, they currently use port 445 (more on this to come).
How Does SMB Work?
The SMB protocol sends and receives request-response messages to establish communication between clients and servers. Port 445 allows SMB to run directly over TCP without NetBIOS, and is used in modern Windows systems.
Is SMB secure?
Newer versions of SMB offer advanced encryption and protections, but SMBv1 is vulnerable to exploits like EternalBlue and should be disabled or patched.
Understanding the SMB Default Port: 445 vs 139 Explained
Introduction to SMB (Server Message Block)
Server Message Block (SMB) is a widely used network protocol that allows shared access to files, printers, and serial ports between nodes on a network.
On Linux:
sudo ufw allow from 192.168.0.0/16 to any port 445 proto tcpAlternatives to SMB fo
SFTP (SSH File Transfer Protocol)
NFS (Network File System)
WebDAVCloud-based sharing (e.g., OneDrive, Google Drive)
These options offer encryption, centralized access control, and better protection for remote sharing.
Conclusion: Proactive SMB Port Security
Understanding the role of ports 445 and 139 is essential for secure SMB implementation.
Furthermore, the WannaCry patch can prevent EternalBlue exploits and similar flaws.
Practice Healthy SMB Habits
It’s better to have layers of security when it comes to protecting yourself from cyberattacks, as it is with other things. Microsoft directory services, often known as Microsoft-DS, use port 445.
TCP and UDP protocols both use port 445 for numerous Microsoft services.
It operates as an application layer network protocol for device communication in Windows operating systems over a network. For example, the Common Internet File System (CIFS) mentioned above is a specific implementation of SMB that enables file sharing. The National Security Agency (NSA) uncovered the flaw in 2017.
The exploit was called EternalBlue, and it was taken from the NSA and posted online by the Shadow Brokers hacker group.
Prior to Windows 2000, most operating systems used TCP 139, with SMB running on top of NetBIOS. WannaCry is a network worm with a transport mechanism designed to spread itself automatically. SMB3 included significant protocol modifications such as the SMB Direct Protocol (SMB over remote direct memory access (RDMA) and SMB Multichannel (many connections per SMB session), which are meant to improve SMB2 performance, particularly in virtualized data centers.
SMB 3.1.1
SMB 3.1.1 was introduced alongside Windows Server 2016 and Windows 10.
Microsoft explained performance issues were primarily because SMB 1.0 is a block-level rather than streaming protocol that was designed for small LANs.
The next dialect, SMB 2.0, improved the protocol's efficiency by reducing its hundreds of commands and subcommand down to 19.
Microsoft continues to invest in improving SMB performance and security.
Microsoft introduced “durable file handles” that allowed the connection to an SMB server to survive brief network failures frequently seen in wireless networks. Microsoft did issue a patch to address the vulnerability, but the WannaCry ransomware attack hit the world just a month later.
More recently, LemonDuck malware has taken advantage of EternalBlue and launched brute-force attacks on SMB services to gain network access.
However, an open port can become a security risk when the service listening to the port is misconfigured, unpatched, vulnerable to exploits, or has poor network security rules.
The most dangerous open ports are wormable ports, like the one that the SMB protocol uses, which are open by default in some operating systems.
Early versions of the SMB protocol were exploited during the WannaCryransomware attack through a zero-day exploit called EternalBlue.
WannaCry exploited legacy versions of Windows computers that used an outdated version of the SMB protocol.
For file replication, user and computer authentication, group policy and trusts, Microsoft Active Directory and Domain Services use this port. NetBIOS is a service on the Open Systems Interconnection (OSI) model’s session layer that allows applications to communicate with one another within a local area network (LAN).