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What Is SMB Protocol?

If you keep up with technology news, you’ve likely come across reports of cyberattacks occurring worldwide, exploiting SMB vulnerabilities. While SMB or Server Message Block protocol might not be familiar to you, as a Windows user, you’re already utilizing it. Therefore, if this raises worries about the security of your Windows system and prompts a desire to understand what SMB is and how secure it proves to be, then please proceed to read the article.

What Is SMB Protocol

What Is SMB Protocol?

The SMB, known as the Server Message Block Protocol, functions as a communication protocol employing a client-server model to facilitate sharing access to files, resources, and communication among network-connected systems. Its purpose is to enable remote opening, editing, sharing, and printing of files across the network. The protocol’s creation aimed to provide a simple and secure means for users within a local area network to easily share and modify files amongst themselves. It was specifically developed to replace earlier Windows file-sharing protocols like CIFS and NFS.

How Does SMB Protocol Work?


The Server Message Block (SMB) protocol operates within a network using a client-server architecture. In this setup, the server stores files or resources that it shares with other computers, referred to as clients, upon their request. SMB is termed a response-request protocol because the client kickstarts the connection by sending an SMB request, to which the server responds with an SMB reply. This establishes a two-way communication channel for sharing resources or files after confirmation.

Working predominantly at the application layer of the network, SMB functions directly over the TCP/IP protocol or other network protocols. There are four primary components integral to SMB operation: the SMB Server (where resources are located), the SMB Client (the requesting system), the SMB Share (the resource to be shared), and the SMB Port (the designated port for operation).

SMB Protocol Versions Development

IBM initially developed the SMB protocol in 1983, which Microsoft later incorporated into Windows. Over time, it has evolved significantly to address emerging challenges. The various iterations of the SMB protocol are referred to as “Dialects.” Presented below is a concise overview of these different dialects:

SMB 1.0

This version of SMB, launched by IBM in 1984 for DOS systems, represents the protocol’s inception. SMB 1.0 integrated the Oplock feature and functioned atop the NetBIOS and TCP/IP interface. However, it suffered from drawbacks such as lacking encryption, extensive communication overhead, and significant security vulnerabilities.

SMB 2.0

Upon the debut of Windows Vista in 2006, SMB 2.0 was introduced, signifying a marked advancement from the earlier SMB 1.0 version. This newer iteration incorporated several improvements, including a reduction in the volume of instructions and commands to decrease excessive communication, support for WAN acceleration, and the implementation of pre-authentication integrity. Unlike SMB 1.0, which utilized a 16-bit data size, SMB 2.0 employed either a 32-bit or 64-bit data size.

SMB 2.1

In 2010, with the launch of Windows 7 and Windows Server 2008 R2, SMB 2.1 made its debut. This version brought about minor enhancements compared to SMB 2.0, particularly in terms of Oplock to improve caching and performance. It also introduced the Maximum Transmission Unit (MTU) support and an enhanced energy-efficient mode to the SMB protocol.

SMB 3.0

In 2012, the release of SMB 3.0 coincided with the launch of Windows 8 and Windows Server 2012. This marked a pivotal update in the SMB protocol, introducing crucial features such as end-to-end encryption, SMB Direct, SMB Multichannel, and support for Remote Volume Shadow Copy Service. These advancements brought about substantial improvements in the performance, security, management, availability, and backup capabilities of the SMB protocol.

SMB 3.02

SMB 3.02 was introduced in 2014, alongside Windows 8.1 and Windows Server 2012 R2, to address the vulnerabilities present in the SMB 1.0 version. This update enabled users to fully deactivate SMB 1.0 on their systems, thereby enhancing security and improving the speed of SMB.

SMB 3.1.1

The most recent significant iteration of SMB is SMB 3.1.1, launched in 2015 alongside Windows 10 and Windows Server 2016. It introduced several enhancements such as advanced AES-128 encryption, directory caching, heightened security against MITM attacks, cluster dialect fencing, and more. The latest Windows 11 also incorporates the SMB 3.1.1 dialect, boasting enhanced features.


CIFS, short for Common Internet File System, represents a variant or dialect of SMB that Microsoft introduced in 1996 alongside Windows 95. While it offered improvements over SMB 1.0, subsequent releases introduced many more enhanced and secure versions of SMB. The following table elucidates the noteworthy distinctions between SMB and CIFS.

Features SMB CIFS
Network Performance The SMB 2.0 and 3.0 versions significantly reduce chattiness, leading to faster speed and improved performance. CIFS is known for its chattiness, causing issues such as slow network performance.
Usability SMB 2.0 reduced required instructions to 19, enhancing overall performance. CIFS demands numerous instructions for file transfer, causing usability challenges due to the complexity of commands.
Authentication Check SMB from version 2.0 introduced pre-authentication checks, requiring a username and password for file access. CIFS lacks pre-authentication checks, allowing open file access during transfers to any user.
Encryption SMB 3.0 and above support advanced end-to-end encryption, including AES-256 encryption for secure data transfer. CIFS lacks encryption, leaving transferred data vulnerable to malicious attacks.
Security Risks SMB 2.0 and higher versions are secure against malware and benefit from advanced encryption. CIFS is vulnerable to malware attacks, as evidenced by instances like NotPetya and WannaCry exploiting its vulnerabilities.


What is the importance of the SMB protocol?

The Server Message Block (SMB) protocol plays a crucial role in network communication, enabling seamless sharing of files, resources, and communication among network-connected systems. It provides a secure and straightforward means for users within a local area network to easily exchange and modify files.

How does the SMB protocol ensure security?

SMB protocol ensures security through various iterations and updates. For instance, newer versions like SMB 3.0 and above support advanced encryption, reducing vulnerabilities and safeguarding data during file transfers. Additionally, it introduces pre-authentication checks in versions like SMB 2.0, requiring user authentication for file access.

What are the key differences between SMB and CIFS in terms of usability?

SMB versions like 2.0 significantly reduced the number of instructions required for file transfer, thereby improving usability. Conversely, CIFS demands numerous and complex instructions, leading to challenges in usability due to the complexity of commands.

How has the SMB protocol evolved over time?

The SMB protocol has undergone significant evolution since its inception in 1983. With various iterations like SMB 2.0, 3.0, and beyond, it has incorporated crucial features such as enhanced encryption, reduced chattiness, improved performance, and increased security measures.

Which versions of the SMB protocol are more secure against potential malware attacks?

Versions such as SMB 2.0 and higher are fortified against malware attacks and benefit from advanced encryption, ensuring a higher level of security. In contrast, CIFS is more susceptible to malware attacks, as observed in incidents like NotPetya and WannaCry that exploited its vulnerabilities.

Why is it essential for Windows users to understand the SMB protocol?

Windows users unknowingly utilize the SMB protocol, making it crucial to comprehend its functionalities and security measures. Understanding SMB helps in recognizing potential vulnerabilities and taking necessary precautions to ensure a secure computing environment.


The evolution of the SMB protocol, from its early stages to the latest SMB 3.1.1, showcases a journey of improvements aimed at enhancing security and performance. Each iteration has introduced crucial features, such as advanced encryption and reduced chattiness, to fortify network security. The contrast between SMB and CIFS underlines critical differences in usability and vulnerability to cyber threats. Understanding these protocols is vital for maintaining secure systems in the face of evolving technological challenges, ensuring efficient file-sharing and robust network security.


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