Server Message Block
Later, Microsoft implemented SMB in Windows NT 3.1 and has been updating it ever since, adapting it to work with newer underlying transports: TCP/IP and NetBT.
In 1996, Microsoft published a version of SMB 1.0[4] with minor modifications under the Common Internet File System (CIFS /sɪfs/) moniker.
[6] Microsoft has since discontinued the CIFS moniker but continues developing SMB and publishing subsequent specifications.
This combination allows file sharing over complex, interconnected networks, including the public Internet.
[2] SMB uses the Kerberos protocol to authenticate users against Active Directory on Windows domain networks.
In the SMB protocol, opportunistic locking is a mechanism designed to improve performance by controlling caching of network files by the client.
[clarification needed] By default, a Microsoft Windows NT 4.0 server used NetBIOS to advertise and locate services.
WINS can still be configured on clients as a secondary name resolution protocol for interoperability with legacy Windows environments and applications.
Further, Microsoft DNS servers can forward name resolution requests to legacy WINS servers in order to support name resolution integration with legacy (pre-Windows 2000) environments that do not support DNS.
Monitoring reveals a high degree of "chattiness" and a disregard of network latency between hosts.
Microsoft has explained that performance issues come about primarily because SMB 1.0 is a block-level rather than a streaming protocol, that was originally designed for small LANs; it has a block size that is limited to 64K, SMB signing creates an additional overhead and the TCP window size is not optimized for WAN links.
[3] Microsoft made considerable modifications to the most commonly used version and included SMB support in the LAN Manager operating system it had started developing for OS/2 with 3Com around 1990.
LAN Manager authentication was implemented based on the original legacy SMB specification's requirement to use IBM "LAN Manager" passwords, but implemented DES in a flawed manner that allowed passwords to be cracked.
SMB1 is an extremely chatty protocol, which is not such an issue on a local area network (LAN) with low latency.
One approach to mitigating the inefficiencies in the protocol is to use WAN optimization products such as those provided by Riverbed, Silver Peak, or Cisco.
[27] In 1996, when Sun Microsystems announced WebNFS,[28] Microsoft launched an initiative to rename SMB to Common Internet File System (CIFS)[3] and added more features, including support for symbolic links, hard links, larger file sizes, and an initial attempt at supporting direct connections over TCP port 445 without requiring NetBIOS as a transport (a largely experimental effort that required further refinement).
It adds the ability to compound multiple actions into a single request, which significantly reduces the number of round-trips the client needs to make to the server, improving performance as a result.
SMB2 uses 32- or 64-bit wide storage fields, and 128 bits in the case of file-handles, thereby removing previous constraints on block sizes, which improves performance with large file transfers over fast networks.
SMB1, originally designed by IBM, was reverse engineered, and later became part of a wide variety of non-Windows operating systems such as Xenix, OS/2 and VMS (Pathworks).
[41] It brought several significant changes that are intended to add functionality and improve SMB2 performance,[42] notably in virtualized data centers: It also introduces several security enhancements, such as end-to-end encryption and a new AES based signing algorithm.
[54] The specifications for the SMB are proprietary and were initially closed, thereby forcing other vendors and projects to reverse-engineer the protocol to interoperate with it.
[55] In 1991, Andrew Tridgell started the development of Samba, a free-software re-implementation (using reverse engineering) of the SMB/CIFS networking protocol for Unix-like systems, initially to implement an SMB server to allow PC clients running the DEC Pathworks client to access files on SunOS machines.
[3][56] Because of the importance of the SMB protocol in interacting with the widespread Microsoft Windows platform, Samba became a popular free software implementation of a compatible SMB client and server to allow non-Windows operating systems, such as Unix-like operating systems, to interoperate with Windows.
NSMB (Netsmb and SMBFS) is a family of in-kernel SMB client implementations in BSD operating systems.
It was first contributed to FreeBSD 4.4 by Boris Popov, and is now found in a wide range of other BSD systems including NetBSD and macOS.
This "Minshall-French" format shows symlinks as textual files with a .symlink extension and a Xsym\n magic number, always 1067 bytes long.
[citation needed] NQ is a family of portable SMB client and server implementations developed by Visuality Systems, an Israel-based company established in 1998 by Sam Widerman, formerly the CEO of Siemens Data Communications.
Likewise developed a CIFS/SMB implementation (versions 1.0, 2.0, 2.1 and SMB 3.0) in 2009 that provided a multiprotocol, identity-aware platform for network access to files used in OEM storage products built on Linux/Unix based devices.
[68] In 2020, two SMB high-severity vulnerabilities were disclosed and dubbed as SMBGhost (CVE-2020-0796) and SMBleed (CVE-2020-1206), which when chained together can provide RCE (Remote Code Execution) privilege to the attacker.
