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	"title": "Server Message Block",
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	"authors": "",
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	"plain_text": "Server Message Block\r\nBy Contributors to Wikimedia projects\r\nPublished: 2003-10-26 · Archived: 2026-04-05 17:40:15 UTC\r\nMap Network Drive dialog in Windows 10, connecting to a local SMB network drive\r\nServer Message Block (SMB) is a communication protocol[1] used to share files, printers, serial ports, and\r\nmiscellaneous communications between nodes on a network. On Windows, the SMB implementation consists of\r\ntwo vaguely named Windows services: \"Server\" (ID: LanmanServer ) and \"Workstation\" (ID:\r\nLanmanWorkstation ).[2]\r\n It uses NTLM or Kerberos protocols for user authentication. It also provides an\r\nauthenticated inter-process communication (IPC) mechanism.\r\nSMB was originally developed in 1983 by Barry A. Feigenbaum at IBM[3] to share access to files and printers\r\nacross a network of systems running IBM PC DOS. In 1987, Microsoft and 3Com implemented SMB in LAN\r\nManager for OS/2, at which time SMB used the NetBIOS service atop the NetBIOS Frames protocol as its\r\nunderlying transport. Later, Microsoft implemented SMB in Windows NT 3.1 and has been updating it ever since,\r\nadapting it to work with newer underlying transports: TCP/IP and NetBT. SMB over QUIC was introduced in\r\nWindows Server 2022.\r\nIn 1996, Microsoft published a version of SMB 1.0[4] with minor modifications under the Common Internet File\r\nSystem (CIFS ) moniker. CIFS was compatible with even the earliest incarnation of SMB, including LAN\r\nManager's.[4] It supports symbolic links, hard links, and larger file size, but none of the features of SMB 2.0 and\r\nlater.\r\n[4][5]\r\n Microsoft's proposal, however, remained an Internet Draft and never achieved standard status.[6]\r\nMicrosoft has since discontinued the CIFS moniker but continues developing SMB and publishing subsequent\r\nspecifications. Samba is a free software reimplementation of the SMB protocol and the Microsoft extensions to it.\r\nServer Message Block (SMB) enables file sharing, printer sharing, network browsing, and inter-process\r\ncommunication (through named pipes) over a computer network. SMB serves as the basis for Microsoft's\r\nDistributed File System implementation.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 1 of 13\n\nSMB relies on the TCP and IP protocols for transport. This combination allows file sharing over complex,\r\ninterconnected networks, including the public Internet. The SMB server component uses TCP port 445. SMB\r\noriginally operated on NetBIOS over IEEE 802.2 - NetBIOS Frames or NBF - and over IPX/SPX, and later on\r\nNetBIOS over TCP/IP (NetBT), but Microsoft has since deprecated these protocols. On NetBT, the server\r\ncomponent uses three TCP or UDP ports: 137 (NETBIOS Name Service), 138 (NETBIOS Datagram Service), and\r\n139 (NETBIOS Session Service).\r\nIn Microsoft Windows, two Windows services implement SMB. The \"Server\" service (ID: LanmanServer ) is in\r\ncharge of serving shared resources. The \"Workstation\" service (ID: LanmanWorkstation ) maintains the computer\r\nname and helps access shared resources on other computers.[2] SMB uses the Kerberos protocol to authenticate\r\nusers against Active Directory on Windows domain networks. On simpler, peer-to-peer networks, SMB uses the\r\nNTLM protocol.\r\nWindows NT 4.0 SP3 and later can digitally sign SMB messages to prevent some man-in-the-middle attacks.\r\n[7][8]\r\n[9]\r\n SMB signing may be configured individually for incoming SMB connections (by the \"LanmanServer\" service)\r\nand outgoing SMB connections (by the \"LanmanWorkstation\" service). The default setting for Windows domain\r\ncontrollers running Windows Server 2003 and later is to not allow unsigned incoming connections.[10] As such,\r\nearlier versions of Windows that do not support SMB signing from the get-go (including Windows 9x) cannot\r\nconnect to a Windows Server 2003 domain controller.\r\n[8]\r\nSMB supports opportunistic locking (see below) on files in order to improve performance. Opportunistic locking\r\nsupport has changed with each Windows Server release.\r\nOpportunistic locking\r\n[edit]\r\nIn the SMB protocol, opportunistic locking is a mechanism designed to improve performance by controlling\r\ncaching of network files by the client.[11] Unlike traditional locks, opportunistic lock (OpLocks) are not strictly\r\nfile locking or used to provide mutual exclusion.\r\nThere are four types of opportunistic locks.\r\nBatch Locks\r\nBatch OpLocks were created originally to support a particular behavior of DOS batch file execution\r\noperation in which the file is opened and closed many times in a short period, which is a performance\r\nproblem. To solve this, a client may ask for an OpLock of type \"batch\". In this case, the client delays\r\nsending the close request and if a subsequent open request is given, the two requests cancel each other.\r\n[12]\r\nLevel-1 OpLocks / Exclusive Locks\r\nWhen an application opens in \"shared mode\" a file hosted on an SMB server which is not opened by any\r\nother process (or other clients) the client receives an exclusive OpLock from the server. This means that\r\nthe client may now assume that it is the only process with access to this particular file, and the client may\r\nnow cache all changes to the file before committing it to the server. This is a performance improvement,\r\nsince fewer round-trips are required in order to read and write to the file. If another client/process tries to\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 2 of 13\n\nopen the same file, the server sends a message to the client (called a break or revocation) which invalidates\r\nthe exclusive lock previously given to the client. The client then flushes all changes to the file.\r\nLevel-2 OpLocks\r\nIf an exclusive OpLock is held by a client and a locked file is opened by a third party, the client has to\r\nrelinquish its exclusive OpLock to allow the other client's write/read access. A client may then receive a\r\n\"Level 2 OpLock\" from the server. A Level 2 OpLock allows the caching of read requests but excludes\r\nwrite caching.\r\nFilter OpLocks\r\nAdded in Windows NT 4.0, Filter Oplocks are similar to Level 2 OpLocks but prevent sharing-mode\r\nviolations between file open and lock reception. Microsoft advises use of Filter OpLocks only where it is\r\nimportant to allow multiple readers and Level 2 OpLocks in other circumstances. Clients holding an\r\nOpLock do not really hold a lock on the file, instead they are notified via a break when another client\r\nwants to access the file in a way inconsistent with their lock. The other client's request is held up while the\r\nbreak is being processed.\r\nBreaks\r\nIn contrast with the SMB protocol's \"standard\" behavior, a break request may be sent from server to client.\r\nIt informs the client that an OpLock is no longer valid. This happens, for example, when another client\r\nwishes to open a file in a way that invalidates the OpLock. The first client is then sent an OpLock break\r\nand required to send all its local changes (in case of batch or exclusive OpLocks), if any, and acknowledge\r\nthe OpLock break. Upon this acknowledgment the server can reply to the second client in a consistent\r\nmanner.\r\nThe use of the SMB protocol has often correlated with a significant increase in broadcast traffic on a network.\r\nHowever the SMB itself does not use broadcasts—the broadcast problems commonly associated with SMB\r\nactually originate with the NetBIOS service location protocol.[clarification needed] By default, a Microsoft Windows\r\nNT 4.0 server used NetBIOS to advertise and locate services. NetBIOS functions by broadcasting services\r\navailable on a particular host at regular intervals. While this usually makes for an acceptable default in a network\r\nwith a smaller number of hosts, increased broadcast traffic can cause problems as the number of hosts on the\r\nnetwork increases. The implementation of name resolution infrastructure in the form of Windows Internet Naming\r\nService (WINS) or Domain Name System (DNS) resolves this problem. WINS was a proprietary implementation\r\nused with Windows NT 4.0 networks, but brought about its own issues and complexities in the design and\r\nmaintenance of a Microsoft network.\r\nSince the release of Windows 2000, the use of WINS for name resolution has been deprecated by Microsoft, with\r\nhierarchical Dynamic DNS now configured as the default name resolution protocol for all Windows operating\r\nsystems. Resolution of (short) NetBIOS names by DNS requires that a DNS client expand short names, usually by\r\nappending a connection-specific DNS suffix to its DNS lookup queries. WINS can still be configured on clients as\r\na secondary name resolution protocol for interoperability with legacy Windows environments and applications.\r\nFurther, Microsoft DNS servers can forward name resolution requests to legacy WINS servers in order to support\r\nname resolution integration with legacy (pre-Windows 2000) environments that do not support DNS.\r\nNetwork designers have found that latency has a significant impact on the performance of the SMB 1.0 protocol,\r\nthat it performs more poorly than other protocols like FTP. Monitoring reveals a high degree of \"chattiness\" and a\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 3 of 13\n\ndisregard of network latency between hosts.[13]\r\n For example, a VPN connection over the Internet will often\r\nintroduce network latency. Microsoft has explained that performance issues come about primarily because SMB\r\n1.0 is a block-level rather than a streaming protocol, that was originally designed for small LANs; it has a block\r\nsize that is limited to 64K, SMB signing creates an additional overhead and the TCP window size is not optimized\r\nfor WAN links.[14] Solutions to this problem include the updated SMB 2.0 protocol,[15] Offline Files, TCP\r\nwindow scaling and WAN optimization devices from various network vendors that cache and optimize SMB\r\n1.0[16] and 2.0.[17]\r\nBarry Feigenbaum originally designed SMB at IBM in early 1983 with the aim of turning DOS INT 21h local file\r\naccess into a networked file system.[3] Microsoft made considerable modifications to the most commonly used\r\nversion and included SMB support in the LAN Manager operating system it had started developing for OS/2 with\r\n3Com around 1990.[18][19][20] Microsoft continued to add features to the protocol in Windows for Workgroups (c. \r\n1992) and in later versions of Windows. LAN Manager authentication was implemented based on the original\r\nlegacy SMB specification's requirement to use IBM \"LAN Manager\" passwords, but implemented DES in a\r\nflawed manner that allowed passwords to be cracked.[21] Later, Kerberos authentication was also added. The\r\nWindows domain logon protocols initially used 40-bit encryption outside of the United States, because of export\r\nrestrictions on stronger 128-bit encryption[22] (subsequently lifted in 1996 when President Bill Clinton signed\r\nExecutive Order 13026[23]).\r\nSMB 1.0 (or SMB1) was originally designed to run on NetBIOS Frames (NetBIOS over IEEE 802.2). Since then,\r\nit has been adapted to NetBIOS over IPX/SPX (NBX), and NetBIOS over TCP/IP (NetBT). Also, since Windows\r\n2000, SMB runs on TCP using TCP port 445, a feature known as \"direct host SMB\".[24] There is still a thin layer\r\n(similar to the Session Message packet of NetBT's Session Service) between SMB and TCP.\r\n[24]\r\n Windows Server\r\n2003, and legacy NAS devices use SMB1 natively.\r\nSMB1 is an extremely chatty protocol, which is not such an issue on a local area network (LAN) with low latency.\r\nIt becomes very slow on wide area networks (WAN) as the back and forth handshake of the protocol magnifies the\r\ninherent high latency of such a network. Later versions of the protocol reduced the high number of handshake\r\nexchanges. One approach to mitigating the inefficiencies in the protocol is to use WAN optimization products such\r\nas those provided by Riverbed, Silver Peak, or Cisco. A better approach is to upgrade to a later version of SMB.\r\nThis includes upgrading both NAS devices as well as Windows Server 2003. The most effective method to\r\nidentify SMB1 traffic is with a network analyzer tool, such as Wireshark. Microsoft also provides an auditing tool\r\nin Windows Server 2016 to track down devices that use SMB1.[25]\r\nMicrosoft marked SMB1 as deprecated in June 2013.[26] Windows Server 2016 and Windows 10 version 1709 do\r\nnot have SMB1 installed by default.[27]\r\nIn 1996, when Sun Microsystems announced WebNFS,\r\n[28]\r\n Microsoft launched an initiative to rename SMB to\r\nCommon Internet File System (CIFS)[3] and added more features, including support for symbolic links, hard links,\r\nlarger file sizes, and an initial attempt at supporting direct connections over TCP port 445 without requiring\r\nNetBIOS as a transport (a largely experimental effort that required further refinement). Microsoft submitted some\r\npartial specifications as Internet Drafts to the IETF.\r\n[6]\r\n These submissions have since expired.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 4 of 13\n\nMicrosoft introduced a new version of the protocol (SMB 2.0 or SMB2) in 2006 with Windows Vista and\r\nWindows Server 2008.\r\n[29]\r\n Although the protocol is proprietary, its specification has been published to allow other\r\nsystems to interoperate with Microsoft operating systems that use the new protocol.[30]\r\nSMB2 reduces the 'chattiness' of the SMB 1.0 protocol by reducing the number of commands and subcommands\r\nfrom over a hundred to just nineteen.[13] It has mechanisms for pipelining, that is, sending additional requests\r\nbefore the response to a previous request arrives, thereby improving performance over high-latency links. It adds\r\nthe 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.[13]\r\n SMB1 also has a compounding\r\nmechanism—known as AndX—to compound multiple actions, but Microsoft clients rarely use AndX.[citation\r\nneeded]\r\n It also introduces the notion of \"durable file handles\": these allow a connection to an SMB server to\r\nsurvive brief network outages, as are typical in a wireless network, without having to incur the overhead of re-negotiating a new session.\r\nSMB2 includes support for symbolic links. Other improvements include caching of file properties, improved\r\nmessage signing with HMAC SHA-256 hashing algorithm and better scalability by increasing the number of\r\nusers, shares and open files per server among others.[13] The SMB1 protocol uses 16-bit data sizes, which\r\namongst other things, limits the maximum block size to 64K. SMB2 uses 32- or 64-bit wide storage fields, and\r\n128 bits in the case of file-handles, thereby removing previous constraints on block sizes, which improves\r\nperformance with large file transfers over fast networks.[13]\r\nWindows Vista/Server 2008 and later operating systems use SMB2 when communicating with other machines also\r\ncapable of using SMB2. SMB1 continues in use for connections with older versions of Windows, as well various\r\nvendors' NAS solutions. Samba 3.5 also includes experimental support for SMB2.[31] Samba 3.6 fully supports\r\nSMB2, except the modification of user quotas using the Windows quota management tools.[32]\r\nWhen SMB2 was introduced it brought a number of benefits over SMB1 for third party implementers of SMB\r\nprotocols. SMB1, originally designed by IBM, was reverse engineered, and later became part of a wide variety of\r\nnon-Windows operating systems such as Xenix, OS/2 and VMS (Pathworks). X/Open standardized it partially;\r\nMicrosoft had submitted Internet-Drafts describing SMB2 to the IETF, partly in response to formal IETF\r\nstandardization of version 4 of the Network File System in December 2000 as IETF RFC 3010;[33] however, those\r\nSMB-related Internet-Drafts expired without achieving any IETF standards-track approval or any other IETF\r\nendorsement. (See http://ubiqx.org/cifs/Intro.html for historical detail.) SMB2 is also a relatively clean break with\r\nthe past. Microsoft's SMB1 code has to work with a large variety of SMB clients and servers. SMB1 features\r\nmany versions of information for commands (selecting what structure to return for a particular request) because\r\nfeatures such as Unicode support were retro-fitted at a later date. SMB2 involves significantly reduced\r\ncompatibility-testing for implementers of the protocol. SMB2 code has considerably less complexity since far less\r\nvariability exists (for example, non-Unicode code paths become redundant as SMB2 requires Unicode support).\r\nApple migrated to SMB2 (from their own Apple Filing Protocol, now legacy) starting with OS X 10.9\r\n\"Mavericks\".\r\n[34]\r\n This transition was fraught with compatibility problems though.[35][36] Non-default support for\r\nSMB2 appeared in fact in OS X 10.7, when Apple abandoned Samba in favor of its own SMB implementation\r\ncalled SMBX[34] after Samba adopted GPLv3.\r\n[37][38]\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 5 of 13\n\nThe Linux kernel's CIFS client file system has SMB2 support since version 3.7.[39]\r\nSMB 2.1, introduced with Windows 7 and Server 2008 R2, introduced minor performance enhancements with a\r\nnew opportunistic locking mechanism.[40]\r\nSMB 3.0 (previously named SMB 2.2)[41] was introduced with Windows 8[41] and Windows Server 2012.\r\n[41]\r\n It\r\nbrought several significant changes that are intended to add functionality and improve SMB2 performance,[42]\r\nnotably in virtualized data centers:\r\nthe SMB Direct Protocol (SMB over remote direct memory access [RDMA])\r\nSMB Multichannel (multiple connections per SMB session),[43][44]\r\nSMB Transparent Failover[45][46]\r\nIt also introduces several security enhancements, such as end-to-end encryption and a new AES based signing\r\nalgorithm.[47][48]\r\nSMB 3.0.2 (known as 3.02 at the time) was introduced with Windows 8.1 and Windows Server 2012 R2;[49][50] in\r\nthose and later releases, the earlier SMB version 1 can be optionally disabled to increase security.\r\n[51][52]\r\nSMB 3.1.1 was introduced with Windows 10 and Windows Server 2016.\r\n[53]\r\n This version supports AES-128 GCM\r\nencryption in addition to AES-128 CCM encryption added in SMB3, and implements pre-authentication integrity\r\ncheck using SHA-512 hash. SMB 3.1.1 also makes secure negotiation mandatory when connecting to clients using\r\nSMB versions that support it.[54]\r\nThe specifications for the SMB are proprietary and were initially closed, thereby forcing other vendors and\r\nprojects to reverse-engineer the protocol to interoperate with it. The SMB 1.0 protocol was eventually published\r\nsome time after it was reverse engineered, whereas the SMB 2.0 protocol was made available from Microsoft's\r\nOpen Specifications Developer Center from the outset.[55]\r\nThird-party implementations\r\n[edit]\r\nThis section needs to be updated. Please help update this article to reflect recent events or newly\r\navailable information. (April 2016)\r\nIn 1991, Andrew Tridgell started the development of Samba, a free-software re-implementation (using reverse\r\nengineering) of the SMB/CIFS networking protocol for Unix-like systems, initially to implement an SMB server\r\nto allow PC clients running the DEC Pathworks client to access files on SunOS machines.[3][56] Because of the\r\nimportance of the SMB protocol in interacting with the widespread Microsoft Windows platform, Samba became\r\na popular free software implementation of a compatible SMB client and server to allow non-Windows operating\r\nsystems, such as Unix-like operating systems, to interoperate with Windows.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 6 of 13\n\nAs of version 3 (2003), Samba provides file and print services for Microsoft Windows clients and can integrate\r\nwith a Windows NT 4.0 server domain, either as a Primary Domain Controller (PDC) or as a domain member.\r\nSamba4 installations can act as an Active Directory domain controller or member server, at Windows 2008\r\ndomain and forest functional levels.[57]\r\nPackage managers in Linux distributions can search for the cifs-utils package. The package is from the Samba\r\nmaintainers.\r\nNSMB (Netsmb and SMBFS) is a family of in-kernel SMB client implementations in BSD operating systems. It\r\nwas first contributed to FreeBSD 4.4 by Boris Popov, and is now found in a wide range of other BSD systems\r\nincluding NetBSD and macOS.\r\n[58]\r\n The implementations have diverged significantly ever since.[59]\r\nThe macOS version of NSMB is notable for its now-common scheme of representing symlinks. This \"Minshall-French\" format shows symlinks as textual files with a .symlink extension and a Xsym\\n magic number, always\r\n1067 bytes long. This format is also used for storing symlinks on native SMB servers or unsupported filesystems.\r\nSamba supports this format with an mfsymlink option.[60] Docker on Windows also seems to use it.[citation\r\nneeded]\r\nNQ is a family of portable SMB client and server implementations developed by Visuality Systems.\r\n[61]\r\n The NQ\r\nfamily comprises an embedded SMB stack (written in C), a Pure Java SMB Client, and a storage SMB server\r\nimplementation. All versions support the SMB 3.1.1 dialect. They support Linux, Windows CE, iOS, Android,\r\nVxWorks and other operating systems.\r\nMoSMB is a user space SMB implementation for Linux. It supports SMB 2.x and SMB 3.x. Key features include\r\nCloud-scale Active-Active Scale-out Clusters, SMB Direct (RDMA), SMB Multichannel, Transparent Failover\r\nand Continuous Availability. MoSMB also supports Amazon S3 object storage as storage backend in addition to\r\nPOSIX file systems such as ext4, ZFS, Lustre, Ceph, etc.[62]\r\nFusion File Share by Tuxera is a proprietary SMB server implementation developed by Tuxera that can be run\r\neither in kernel or user space.\r\n[63]\r\n It supports SMB 3.1.1 and all previous versions, additionally advanced SMB\r\nfeatures like continuous availability (persistent handles) scale-out, RDMA (SMB Direct), SMB multichannel,\r\ntransparent compression, shadow copy.\r\nLikewise developed a CIFS/SMB implementation (versions 1.0, 2.0, 2.1 and SMB 3.0) in 2009 that provided a\r\nmultiprotocol, identity-aware platform for network access to files used in OEM storage products built on\r\nLinux/Unix based devices. The platform could be used for traditional NAS, Cloud Gateway, and Cloud Caching\r\ndevices for providing secure access to files across a network. Likewise was purchased by EMC Isilon in 2012.\r\nKSMBD is an open source in-kernel CIFS/SMB server implementation for the Linux kernel. Compared to user-space implementations, it provides better performance and makes it easier to implement some features such as\r\nSMB Direct. It supports SMB 3.1.1 and previous versions.\r\nOver the years, there have been many security vulnerabilities in Microsoft's implementation of the protocol or\r\ncomponents on which it directly relies.[64][65] Other vendors' security vulnerabilities lie primarily in a lack of\r\nsupport for newer authentication protocols like NTLMv2 and Kerberos in favor of protocols like NTLMv1,\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 7 of 13\n\nLanMan, or plaintext passwords. Real-time attack tracking[66]\r\n shows that SMB is one of the primary attack\r\nvectors for intrusion attempts,[67] for example the 2014 Sony Pictures attack,\r\n[68]\r\n and the WannaCry ransomware\r\nattack of 2017.[69] In 2020, two SMB high-severity vulnerabilities were disclosed and dubbed as SMBGhost\r\n(CVE-2020-0796) and SMBleed (CVE-2020-1206), which when chained together can provide RCE (Remote\r\nCode Execution) privilege to the attacker.\r\n[70]\r\nList of products that support SMB\r\nAdministrative share\r\nShared file access\r\nAppleTalk\r\nNetwork File System (protocol)\r\nRemote File System\r\nWebDAV\r\nUniform Naming Convention\r\nNetwork Neighborhood\r\n1. ^ \"Microsoft SMB Protocol and CIFS Protocol Overview\". Microsoft. October 22, 2009. Archived from the\r\noriginal on August 2, 2016. Retrieved April 10, 2019.\r\n2. ^ Jump up to: a\r\n \r\nb\r\n \"Lan Manager Networking Concepts\". Support. Microsoft. Archived from the original on\r\nDecember 30, 2012. Retrieved September 18, 2014.\r\n3. ^ Jump up to: a\r\n \r\nb\r\n \r\nc\r\n \r\nd\r\n Tridgell, Andrew. \"Myths About Samba\". Archived from the original on October 20,\r\n2017. Retrieved January 3, 2016.\r\n4. ^ Jump up to: a\r\n \r\nb\r\n \r\nc\r\n \"Common Internet File System\". Windows 2000 Web and Application Services Technical\r\nOverview. Microsoft. 18 July 2012. Archived from the original on 30 January 2022. Retrieved 30 January\r\n2022 – via Microsoft Docs.\r\n5. ^ Coulter, David; Satran, Michael; Batchelor, Drew (8 January 2021). \"Microsoft SMB Protocol and CIFS\r\nProtocol Overview\". Windows App Development. Microsoft. Archived from the original on 28 January\r\n2022. Retrieved 30 January 2022 – via Microsoft Docs.\r\n6. ^ Jump up to: a\r\n \r\nb\r\n See:\r\nHeizer, I.; Leach, P.; Perry, D. (June 13, 1996). \"Common Internet File System Protocol\r\n(CIFS/1.0)\". Archived from the original on August 8, 2019.\r\nLeach, Paul J.; Naik, Dilip C. (January 3, 1997). \"CIFS Logon and Pass Through Authentication\".\r\nArchived from the original on May 31, 2024. Retrieved December 10, 2017.\r\nLeach, Paul J.; Naik, Dilip C. (January 10, 1997). \"CIFS/E Browser Protocol\". Archived from the\r\noriginal on May 31, 2024. Retrieved December 10, 2017.\r\nLeach, Paul J.; Naik, Dilip C. (January 31, 1997). \"CIFS Printing Specification\". Archived from the\r\noriginal on May 31, 2024. Retrieved December 10, 2017.\r\nLeach, Paul J.; Naik, Dilip C. (February 26, 1997). \"CIFS Remote Administration Protocol\".\r\nArchived from the original on May 31, 2024. Retrieved December 10, 2017.\r\nLeach, Paul J.; Naik, Dilip C. (December 19, 1997). \"A Common Internet File System (CIFS/1.0)\r\nProtocol\". Archived from the original on May 31, 2024. Retrieved December 10, 2017.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 8 of 13\n\n7. ^ \"Overview of Server Message Block signing\". Windows Server troubleshooting. Microsoft. 24 November\r\n2021. Archived from the original on 29 January 2022. Retrieved 29 January 2022 – via Microsoft Docs.\r\n8. ^ Jump up to: a\r\n \r\nb\r\n Johansson, Jesper M. (20 May 2005). \"How to Shoot Yourself in the Foot with Security,\r\nPart 1\". Security Guidance. Microsoft. Archived from the original on 19 October 2018. Retrieved 19\r\nOctober 2018 – via Microsoft Docs. “This article addresses [...] Server Message Block (SMB) message\r\nsigning.”\r\n9. ^ Barreto, Jose (1 December 2010). \"The Basics of SMB Signing (covering both SMB1 and SMB2)\". Jose\r\nBarreto's Blog Archive. Microsoft. Archived from the original on 2 December 2012 – via Microsoft Docs.\r\n“This security mechanism in the SMB protocol helps avoid issues like tampering of packets and \"man in\r\nthe middle\" attacks. [...] SMB signing is available in all currently supported versions of Windows, but it's\r\nonly enabled by default on Domain Controllers. This is recommended for Domain Controllers because\r\nSMB is the protocol used by clients to download Group Policy information. SMB signing provides a way to\r\nensure that the client is receiving genuine Group Policy.”\r\n10. ^ \"MSKB887429: Overview of Server Message Block signing\". Microsoft. November 30, 2007. Archived\r\nfrom the original on November 20, 2010. Retrieved October 24, 2012. “By default, SMB signing is\r\nrequired for incoming SMB sessions on Windows Server 2003-based domain controllers.”\r\n11. ^ \"Opportunistic Locks\". Microsoft. May 31, 2018. Archived from the original on August 19, 2021.\r\nRetrieved August 19, 2021.\r\n12. ^ \"All About Opportunistic Locking\". Sphere IT. 2014. Archived from the original on August 19, 2021.\r\nRetrieved August 19, 2021.\r\n13. ^ Jump up to: a\r\n \r\nb\r\n \r\nc\r\n \r\nd\r\n \r\ne\r\n Jose Barreto (December 9, 2008). \"SMB2, a Complete Redesign of the Main Remote\r\nFile Protocol for Windows\". Microsoft Server \u0026 Management Blogs. Archived from the original on\r\nJanuary 12, 2013. Retrieved November 1, 2009.\r\n14. ^ Neil Carpenter (October 26, 2004). \"SMB/CIFS Performance Over WAN Links\". Microsoft. Archived\r\nfrom the original on February 13, 2020. Retrieved February 13, 2020.\r\n15. ^ \"What's New in SMB in Windows Server\". Microsoft. 31 August 2016. Archived from the original on\r\nFebruary 11, 2017. Retrieved 6 February 2017.\r\n16. ^ Mark Rabinovich, Igor Gokhman. \"CIFS Acceleration Techniques\" (PDF). Storage Developer\r\nConference, SNIA, Santa Clara 2009. Archived (PDF) from the original on September 30, 2020. Retrieved\r\nJuly 6, 2020.\r\n17. ^ Mark Rabinovich. \"Accelerating SMB2\" (PDF). Storage Developer Conference, SNIA, Santa Clara 2011.\r\nArchived (PDF) from the original on May 31, 2024. Retrieved July 6, 2020.\r\n18. ^ Speed, Richard. \"Have to use SMB 1.0? Windows 10 April 2018 Update says NO\". theregister.com.\r\nArchived from the original on 18 February 2023. Retrieved 18 February 2023.\r\n19. ^ guenni (15 June 2017). \"Microsoft plans to deactivate SMBv1 in Windows 10 V1709\". Born's Tech and\r\nWindows World. Archived from the original on 18 February 2023. Retrieved 18 February 2023.\r\n20. ^ Giret, Laurent (20 April 2022). \"Microsoft Gets Ready to Disable SMB1 Protocol on Windows 11\".\r\nThurrott.com. Archived from the original on 31 May 2024. Retrieved 18 February 2023.\r\n21. ^ Christopher Hertel (1999). \"SMB: The Server Message Block Protocol\". Archived from the original on\r\nMarch 10, 2010. Retrieved November 1, 2009.\r\n22. ^ \"Description of Microsoft Windows Encryption Pack 1\". Microsoft. November 1, 2006. Archived from the\r\noriginal on October 2, 2009. Retrieved November 1, 2009.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 9 of 13\n\n23. ^ \"US Executive Order 13026\" (PDF). United States Government. 1996. Archived (PDF) from the original\r\non October 10, 2009. Retrieved November 1, 2009.\r\n24. ^ Jump up to: a\r\n \r\nb\r\n \"Direct hosting of SMB over TCP/IP\". Microsoft. October 11, 2007. Archived from the\r\noriginal on March 26, 2011. Retrieved November 1, 2009.\r\n25. ^ Kyttle, Ralph (13 May 2017). \"SMB1 – Audit Active Usage using Message Analyzer\". Microsoft TechNet.\r\nMicrosoft. Archived from the original on March 28, 2019. Retrieved 28 March 2019.\r\n26. ^ \"The Deprecation of SMB1 – You should be planning to get rid of this old SMB dialect – Jose Barreto's\r\nBlog\". blogs.technet.microsoft.com. 21 April 2015. Archived from the original on May 21, 2017. Retrieved\r\n2019-10-09.\r\n27. ^ \"SMBv1 is not installed by default in Windows 10 Fall Creators Update and Windows Server, version\r\n1709 and later versions\". support.microsoft.com. 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Archived from the original on September 11, 2016. Retrieved\r\nSeptember 4, 2016.\r\n40. ^ \"Implementing an End-User Data Centralization Solution\". Microsoft. October 21, 2009. pp. 10–11.\r\nArchived from the original on September 6, 2010. Retrieved November 2, 2009.\r\n41. ^ Jump up to: a\r\n \r\nb\r\n \r\nc\r\n Jeffrey Snover (April 19, 2012). \"SMB 2.2 is now SMB 3.0\". Windows Server Blog.\r\nArchived from the original on July 8, 2020. Retrieved July 6, 2020.\r\n42. ^ Chelsio Communications (2 April 2013). \"40G SMB Direct\". Archived from the original on September 7,\r\n2013. Retrieved June 18, 2013.\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 10 of 13\n\n43. ^ Jose Barreto (October 19, 2012). \"SNIA Tutorial on the SMB Protocol\" (PDF). Storage Networking\r\nIndustry Association. Archived (PDF) from the original on June 3, 2013. Retrieved November 28, 2012.\r\n44. ^ Thomas Pfenning. \"The Future of File Protocols: SMB 2.2 in the Datacenter\" (PDF). 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Retrieved\r\nAugust 14, 2016.\r\n49. ^ Jose Barreto (July 7, 2014). \"Updated Links on Windows Server 2012 R2 File Server and SMB 3.02\".\r\nMicrosoft TechNet Server \u0026 Management Blogs. Archived from the original on August 26, 2016. Retrieved\r\nAugust 14, 2016.\r\n50. ^ Jose Barreto (December 12, 2013). \"Storage Developer Conference – SDC 2013 slides now publicly\r\navailable. Here are the links to Microsoft slides…\". Microsoft TechNet Server \u0026 Management Blogs.\r\nArchived from the original on August 26, 2016. Retrieved August 14, 2016.\r\n51. ^ Eric Geier (December 5, 2013). \"WindowsNetworking.com: Improvements in the SMB 3.0 and 3.02\r\nProtocol Updates\". WindowsNetworking.com. Archived from the original on April 9, 2015. Retrieved April\r\n6, 2015.\r\n52. ^ Jose Barreto (April 30, 2015). \"SMB3 Networking Links for Windows Server 2012 R2\". Microsoft\r\nTechNet Server \u0026 Management Blogs. Archived from the original on August 26, 2016. Retrieved August\r\n14, 2016.\r\n53. ^ Jose Barreto (May 5, 2015). \"What's new in SMB 3.1.1 in the Windows Server 2016 Technical Preview\r\n2\". Microsoft TechNet Server \u0026 Management Blogs. Archived from the original on October 8, 2016.\r\nRetrieved August 14, 2016.\r\n54. ^ \"SMB security enhancements\". Microsoft Learn. Archived from the original on 2023-04-10. Retrieved\r\n2023-04-10.\r\n55. ^ \"Windows Protocols\". Archived from the original on September 26, 2009. Retrieved October 13, 2009.\r\n56. ^ Tridgell, Andrew (June 27, 1997). \"A bit of history and a bit of fun\". Archived from the original on July\r\n17, 2011. Retrieved July 26, 2011.\r\n57. ^ \"Samba 4 functional levels\". February 25, 2011. Archived from the original on July 29, 2014. Retrieved\r\nJanuary 12, 2014.\r\n58. ^ \"netsmb(4)\". NetBSD 8.0 manual pages. Archived from the original on 17 November 2022. Retrieved 5\r\nJanuary 2020.\r\n59. ^ nsmb.conf(5)  – FreeBSD File Formats Manual.\r\n60. ^ \"UNIX Extensions\". SambaWiki. Archived from the original on June 12, 2020. Retrieved March 15, 2020.\r\n61. ^ https://www.visualitynq.com\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 11 of 13\n\n62. ^ Sunu Engineer. \"Building a Highly Scalable and Performant SMB Protocol Server\" (PDF). Archived\r\n(PDF) from the original on September 27, 2016. Retrieved September 25, 2016.\r\n63. ^ \"Microsoft and Tuxera strengthen partnership through Tuxera SMB Server\". Microsoft. Microsoft News\r\nCenter. 14 September 2016. Archived from the original on November 17, 2016. Retrieved 6 February 2017.\r\n64. ^ \"MS02-070: Flaw in SMB Signing May Permit Group Policy to Be Modified\". Microsoft. December 1,\r\n2007. Archived from the original on October 8, 2009. Retrieved November 1, 2009.\r\n65. ^ \"MS09-001: Vulnerabilities in SMB could allow remote code execution\". Microsoft. January 13, 2009.\r\nArchived from the original on October 5, 2009. Retrieved November 1, 2009.,\r\n66. ^ \"Sicherheitstacho.eu\". Deutsche Telekom. March 7, 2013. Archived from the original on March 8, 2013.\r\nRetrieved March 7, 2013.\r\n67. ^ \"Alert (TA14-353A) Targeted Destructive Malware\". US-CERT. Archived from the original on December\r\n20, 2014. Retrieved December 20, 2014.\r\n68. ^ \"Sony Hackers Used Server Message Block (SMB) Worm Tool\". 19 December 2014. Archived from the\r\noriginal on December 20, 2014. Retrieved December 20, 2014.\r\n69. ^ \"WannaCry Ransomware Attack Hits Victims With Microsoft SMB Exploit\". eWeek. Retrieved 13 May\r\n2017.\r\n70. ^ \"SMBleedingGhost Writeup: Chaining SMBleed (CVE-2020-1206) with SMBGhost\". Jamf Blog. 2020-\r\n06-09. Retrieved 2020-11-19.\r\n\"[MS-CIFS]: Common Internet File System (CIFS) Protocol\". Open Specifications. Microsoft. 30 October\r\n2020.\r\nSpecifies the Common Internet File System (CIFS) Protocol, a cross-platform, transport-independent protocol that provides a mechanism for client systems to use file and print services\r\nmade available by server systems over a network\r\n\"[MS-SMB]: Server Message Block (SMB) Protocol\". Open Specifications. Microsoft. 25 June 2021.\r\nSpecifies the Server Message Block (SMB) Protocol, which defines extensions to the existing\r\nCommon Internet File System (CIFS) specification that have been implemented by Microsoft since\r\nthe publication of the CIFS specification.\r\n\"[MS-SMB2]: Server Message Block (SMB) Protocol Versions 2 and 3\". Open Specifications. Microsoft. 14\r\nDecember 2021.\r\nSpecifies the Server Message Block (SMB) Protocol Versions 2 and 3, which support the sharing of\r\nfile and print resources between machines and extend the concepts from the Server Message Block\r\nProtocol.\r\n\"[MS-SMBD]: SMB2 Remote Direct Memory Access (RDMA) Transport Protocol\". Open Specifications.\r\nMicrosoft. 25 June 2021.\r\nSpecifies the SMB2 Remote Direct Memory Access (RDMA) Transport Protocol, a wrapper for the\r\nexisting SMB2 protocol that allows SMB2 packets to be delivered over RDMA-capable transports\r\nsuch as iWARP or Infiniband while utilizing the direct data placement (DDP) capabilities of these\r\ntransports. Benefits include reduced CPU overhead, lower latency, and improved throughput.\r\nHertel, Christopher (2003). Implementing CIFS – The Common Internet FileSystem Archived 2004-02-02\r\nat the Wayback Machine. Prentice Hall. ISBN 0-13-047116-X. (Text licensed under the Open Publication\r\nLicense, v1.0 or later, available from the link above.)\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 12 of 13\n\nSteven M. French, A New Network File System is Born: Comparison of SMB2, CIFS, and NFS Archived\r\n2012-09-07 at the Wayback Machine, Linux Symposium 2007\r\nSteve French, The Future of File Protocols: SMB2 Meets Linux Archived 2018-08-17 at the Wayback\r\nMachine, Linux Collaboration Summit 2012\r\nDFS section in \"Windows Developer\" documentation\r\nthe NT LM 0.12 dialect of SMB. In Microsoft Word format\r\nSource: https://en.wikipedia.org/wiki/Server_Message_Block\r\nhttps://en.wikipedia.org/wiki/Server_Message_Block\r\nPage 13 of 13\n\n7. ^ \"Overview of Server Message https://en.wikipedia.org/wiki/Server_Message_Block Block signing\". Windows Server troubleshooting. Microsoft. 24 November\n2021. Archived from the original on 29 January 2022. Retrieved 29 January 2022-via Microsoft Docs.\n8. ^ Jump up to: a b Johansson, Jesper M. (20 May 2005). \"How to Shoot Yourself in the Foot with Security,\nPart 1\". Security Guidance. Microsoft. Archived from the original on 19 October 2018. Retrieved 19\nOctober 2018-via Microsoft Docs. “This article addresses [...] Server Message Block (SMB) message\nsigning.”      \n9. ^ Barreto, Jose (1 December 2010). \"The Basics of SMB Signing (covering both SMB1 and SMB2)\". Jose\nBarreto's Blog Archive. Microsoft. Archived from the original on 2 December 2012-via Microsoft Docs.\n“This security mechanism in the SMB protocol helps avoid issues like tampering of packets and \"man in\nthe middle\" attacks. [...] SMB signing is available in all currently supported versions of Windows, but it's\nonly enabled by default on Domain Controllers. This is recommended for Domain Controllers because\nSMB is the protocol used by clients to download Group Policy information. SMB signing provides a way to\nensure that the client is receiving genuine Group Policy.”   \n10. ^ \"MSKB887429: Overview of Server Message Block signing\". Microsoft. November 30, 2007. Archived\nfrom the original on November 20, 2010. Retrieved October 24, 2012. “By default, SMB signing is\nrequired for incoming SMB sessions on Windows Server 2003-based domain controllers.” \n11. ^ \"Opportunistic Locks\". Microsoft. May 31, 2018. Archived from the original on August 19, 2021.\nRetrieved August 19, 2021.     \n12. ^ \"All About Opportunistic Locking\". Sphere IT. 2014. Archived from the original on August 19, 2021.\nRetrieved August 19, 2021.     \n13. ^ Jump up to: a b c d e Jose Barreto (December 9, 2008). \"SMB2, a Complete Redesign of the Main Remote\nFile Protocol for Windows\". Microsoft Server \u0026 Management Blogs. Archived from the original on\nJanuary 12, 2013. Retrieved November 1, 2009.    \n14. ^ Neil Carpenter (October 26, 2004). \"SMB/CIFS Performance Over WAN Links\". Microsoft. Archived\nfrom the original on February 13, 2020. Retrieved February 13, 2020.  \n15. ^ \"What's New in SMB in Windows Server\". Microsoft. 31 August 2016. Archived from the original on\nFebruary 11, 2017. Retrieved 6 February 2017.    \n16. ^ Mark Rabinovich, Igor Gokhman. \"CIFS Acceleration Techniques\" (PDF). Storage Developer \nConference, SNIA, Santa Clara 2009. Archived (PDF) from the original on September 30, 2020. Retrieved\nJuly 6, 2020.      \n17. ^ Mark Rabinovich. \"Accelerating SMB2\" (PDF). Storage Developer Conference, SNIA, Santa Clara 2011.\nArchived (PDF) from the original on May 31, 2024. Retrieved July 6, 2020.  \n18. ^ Speed, Richard. \"Have to use SMB 1.0? Windows 10 April 2018 Update says NO\". theregister.com. \nArchived from the original on 18 February 2023. Retrieved 18 February 2023.  \n19. ^ guenni (15 June 2017). \"Microsoft plans to deactivate SMBv1 in Windows 10 V1709\". Born's Tech and\nWindows World. Archived from the original on 18 February 2023. Retrieved 18 February 2023. \n20. ^ Giret, Laurent (20 April 2022). \"Microsoft Gets Ready to Disable SMB1 Protocol on Windows 11\".\nThurrott.com. Archived from the original on 31 May 2024. Retrieved 18 February 2023. \n21. ^ Christopher Hertel (1999). \"SMB: The Server Message Block Protocol\". Archived from the original on\nMarch 10, 2010. Retrieved November 1, 2009.    \n22. ^ \"Description of Microsoft Windows Encryption Pack 1\". Microsoft. November 1, 2006. Archived from the\noriginal on October 2, 2009. Retrieved November 1, 2009.   \n   Page 9 of 13",
	"extraction_quality": 1,
	"language": "EN",
	"sources": [
		"MITRE"
	],
	"origins": [
		"web"
	],
	"references": [
		"https://en.wikipedia.org/wiki/Server_Message_Block"
	],
	"report_names": [
		"Server_Message_Block"
	],
	"threat_actors": [],
	"ts_created_at": 1775434300,
	"ts_updated_at": 1775826780,
	"ts_creation_date": 0,
	"ts_modification_date": 0,
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