CIFS vs. SMB: what they are, how they differ, and why it matters for file share security

If your organization uses file sharing (and it does), you've probably seen the terms CIFS and SMB tossed around in networking docs, NAS device menus, and storage vendor interfaces. They're often treated as synonyms. They aren't. CIFS is a specific, outdated dialect of the broader SMB protocol family, and knowing the difference has real implications for both performance and security.

This page breaks down what each protocol is, how they evolved, where they diverge, and what your security team should know about auditing file share activity over SMB. If your environment includes Windows file servers or NAS devices, you'll also see how ManageEngine ADAudit Plus provides real-time auditing of file share access without the headache of parsing raw Windows event logs.

What is SMB?

Server Message Block (SMB) is a network protocol that lets nodes on a network share access to files, printers, and serial ports. IBM created SMB in 1983, and Microsoft later adopted and extended it as the default file-sharing protocol in Windows environments.

SMB is a client-server protocol: the client requests access to a resource, and the server provides it. An SMB share is a file, folder, or printer resource made accessible over a network using this protocol. Client machines connect to the share to read, write, or manage files.

SMB is most closely associated with Windows, but it's also supported on Linux (via Samba) and macOS. That cross-platform support makes it the most widely used file-sharing protocol in mixed-OS enterprise environments.

What is CIFS?

Common Internet File System (CIFS) is a specific dialect, or version, of SMB. Microsoft introduced CIFS in the mid-1990s as an extension of SMB 1.0, designed to work over the internet. CIFS added several features over the original SMB specification:

• File locking mechanisms for concurrent access
• Support for larger file sizes
• Transport over TCP/IP (port 445), removing the dependency on NetBIOS

Here's the thing that trips people up: CIFS is essentially SMB 1.0 with enhancements. It is not a separate protocol family. When someone references "CIFS," they're almost always talking about SMB 1.0.

CIFS is technically obsolete. Most modern operating systems no longer support CIFS (SMB 1.0) by default because of well-documented security vulnerabilities and poor performance.

SMB version history

The SMB protocol has changed considerably since its origins. The table below summarizes each major version and what it introduced:

SMB 3.1.1 is the current version and is highly secure when properly configured.

How CIFS and modern SMB actually differ

The gap between CIFS (SMB 1.0) and modern SMB versions is wide, and it spans performance, security, authentication, and platform support:

When you see "CIFS/SMB" in vendor documentation or device configuration menus, the underlying protocol in use is typically a modern SMB version, not the original CIFS implementation.

Is CIFS still used today?

The short answer: the term is, but the protocol mostly isn't.

The word "CIFS" still shows up in networking documentation, NAS device configuration menus, and storage vendor interfaces. In practice, most devices advertising "CIFS" support are actually running SMB 2.x or 3.x under the hood.

SMB 1.0/CIFS is disabled by default in Windows 10 (version 1709+), Windows 11, and Windows Server 2019+. Microsoft has actively encouraged disabling SMB 1.0 since 2017 following the WannaCry ransomware attack, which exploited an SMB 1.0 vulnerability to spread across networks worldwide.

If your environment still has SMB 1.0/CIFS enabled, disable it and migrate to SMB 3.x. Audit your network first to identify systems that still depend on SMB 1.0 so you don't break legacy applications or devices in the process.

CIFS, SMB, Samba, and NFS: how they relate

Several related terms come up alongside CIFS and SMB in networking conversations. Here's how they fit together:

Samba is an open-source implementation of the SMB protocol for Linux and Unix systems. It lets Linux and Unix machines participate in Windows file sharing. Samba is not a separate protocol; it implements SMB.

NFS (Network File System) is a different protocol entirely, developed by Sun Microsystems, and is primarily used in Unix and Linux environments. Many enterprises run both SMB and NFS. Which one you choose depends on your operating system environment and security requirements.

The following table compares SMB and NFS across a few dimensions:

Security risks of running legacy CIFS (SMB 1.0)

Organizations that still run CIFS (SMB 1.0) face several well-documented security risks:

• No encryption: Data travels in plaintext, which means anyone on the network can intercept it.
• Weak authentication: NTLMv1 is susceptible to credential theft and relay attacks.
• Known exploits: EternalBlue (CVE-2017-0144) is the most infamous vulnerability in SMB 1.0. It was used in the WannaCry and NotPetya ransomware activity campaigns.
• No integrity verification: Without pre-authentication integrity checks, connections are vulnerable to downgrade attacks that force negotiation to weaker protocol versions.
• No audit trail by default: Native Windows auditing of SMB 1.0 file access requires manual configuration and generates verbose, hard-to-parse security event logs.

Disabling SMB 1.0 is the first step. The second is making sure you actually have visibility into who is accessing your file shares over SMB, and what they're doing with that access.

How to audit SMB file share access with ADAudit Plus

Whether your file servers run SMB 2.x or 3.x, auditing file share access matters for catching unauthorized access, insider threats, and ransomware behavior. ADAudit Plus provides real-time auditing of file share activity across Windows file servers and 13 NAS device types, without the overhead of parsing raw Windows event logs.

Here's what ADAudit Plus gives you:

Who accessed what, and when. Every file read, create, modify, delete, move, rename, and copy-paste event is captured with the user, client machine, client IP, file path, and timestamp. The All File or Folder Changes report provides a complete file activity trail across your environment.

Permission change tracking. Folder permission changes (DACL) are logged with old and new values. Folder audit setting (SACL) changes and folder ownership changes are tracked separately, so you get full visibility into who can access what.

Failed access attempts. Failed attempts to read, write, or delete files are captured in dedicated reports. These events often indicate unauthorized access attempts or privilege misconfiguration and are worth investigating.

UBA-driven anomaly detection. The user behavior analytics engine uses machine learning to baseline normal file activity per user. It then flags deviations: unusual file activity volume, unusual file modification spikes (a strong ransomware indicator), unusual file deletion spikes, and file access at unusual times.

Real-time alerts. Pre-configured alert profiles cover file deletion, folder permission changes, file integrity monitoring events, and GDPR-sensitive share access. Alerts can trigger email or SMS notifications along with automated incident response actions.

NAS device coverage. In addition to Windows file servers and failover clusters, ADAudit Plus audits file activity on NetApp, EMC Isilon, Synology, Hitachi, Huawei, QNAP, Amazon FSx, Azure File Share, CTERA, Nutanix, and Qumulo from a single NAS auditing console.

Compliance-ready reports. Pre-configured compliance reports map to SOX, HIPAA, PCI-DSS, GDPR, FISMA, GLBA, and ISO 27001, which cuts down the effort required to prepare for audits.

Frequently asked questions