Remote Services: SMB/Windows Admin Shares

Adversaries may use Valid Accounts to interact with a remote network share using Server Message Block (SMB). The adversary may then perform actions as the logged-on user.

SMB is a file, printer, and serial port sharing protocol for Windows machines on the same network or domain. Adversaries may use SMB to interact with file shares, allowing them to move laterally throughout a network. Linux and macOS implementations of SMB typically use Samba.

Windows systems have hidden network shares that are accessible only to administrators and provide the ability for remote file copy and other administrative functions. Example network shares include C$, ADMIN$, and IPC$. Adversaries may use this technique in conjunction with administrator-level Valid Accounts to remotely access a networked system over SMB,[1] to interact with systems using remote procedure calls (RPCs),[2] transfer files, and run transferred binaries through remote Execution. Example execution techniques that rely on authenticated sessions over SMB/RPC are Scheduled Task/Job, Service Execution, and Windows Management Instrumentation. Adversaries can also use NTLM hashes to access administrator shares on systems with Pass the Hash and certain configuration and patch levels.[3]

ID: T1021.002
Sub-technique of:  T1021
Platforms: Windows
System Requirements: SMB enabled; Host/network firewalls not blocking SMB ports between source and destination; Use of domain account in administrator group on remote system or default system admin account.
Version: 1.2
Created: 11 February 2020
Last Modified: 28 July 2023

Procedure Examples

ID Name Description
C0025 2016 Ukraine Electric Power Attack

During the 2016 Ukraine Electric Power Attack, Sandworm Team utilized net use to connect to network shares.[4]

S0504 Anchor

Anchor can support windows execution via SMB shares.[5]

G0007 APT28

APT28 has mapped network drives using Net and administrator credentials.[6]

G0022 APT3

APT3 will copy files over to Windows Admin Shares (like ADMIN$) as part of lateral movement.[7]

G0050 APT32

APT32 used Net to use Windows' hidden network shares to copy their tools to remote machines for execution.[8]

G0087 APT39

APT39 has used SMB for lateral movement.[9]

G0096 APT41

APT41 has transferred implant files using Windows Admin Shares.[10]

S0089 BlackEnergy

BlackEnergy has run a plug-in on a victim to spread through the local network by using PsExec and accessing admin shares.[11]

G0108 Blue Mockingbird

Blue Mockingbird has used Windows Explorer to manually copy malicious files to remote hosts over SMB.[12]

S1063 Brute Ratel C4

Brute Ratel C4 has the ability to use SMB to pivot in compromised networks.[13][14][15]

G0114 Chimera

Chimera has used Windows admin shares to move laterally.[16][17]

G1021 Cinnamon Tempest

Cinnamon Tempest has used SMBexec for lateral movement.[18]

S0154 Cobalt Strike

Cobalt Strike can use Window admin shares (C$ and ADMIN$) for lateral movement.[19][20]

S0608 Conficker

Conficker variants spread through NetBIOS share propagation.[21]

S0575 Conti

Conti can spread via SMB and encrypts files on different hosts, potentially compromising an entire network.[22][23]

C0029 Cutting Edge

During Cutting Edge, threat actors moved laterally using compromised credentials to connect to internal Windows systems with SMB.[24]

G0009 Deep Panda

Deep Panda uses net.exe to connect to network shares using net use commands with compromised credentials.[25]

S0659 Diavol

Diavol can spread throughout a network via SMB prior to encryption.[26]

S0038 Duqu

Adversaries can instruct Duqu to spread laterally by copying itself to shares it has enumerated and for which it has obtained legitimate credentials (via keylogging or other means). The remote host is then infected by using the compromised credentials to schedule a task on remote machines that executes the malware.[27]

S0367 Emotet

Emotet has leveraged the Admin$, C$, and IPC$ shares for lateral movement. [28][29]

G1016 FIN13

FIN13 has leveraged SMB to move laterally within a compromised network via application servers and SQL servers.[30]

G0061 FIN8

FIN8 has attempted to map to C$ on enumerated hosts to test the scope of their current credentials/context. FIN8 has also used smbexec from the Impacket suite for lateral movement.[31][32]

G0117 Fox Kitten

Fox Kitten has used valid accounts to access SMB shares.[33]

S0698 HermeticWizard

HermeticWizard can use a list of hardcoded credentials to to authenticate via NTLMSSP to the SMB shares on remote systems.[34]

G0004 Ke3chang

Ke3chang actors have been known to copy files to the network shares of other computers to move laterally.[35][36]

S0236 Kwampirs

Kwampirs copies itself over network shares to move laterally on a victim network.[37]

G0032 Lazarus Group

Lazarus Group malware SierraAlfa accesses the ADMIN$ share via SMB to conduct lateral movement.[38][39]

S0532 Lucifer

Lucifer can infect victims by brute forcing SMB.[40]

G1009 Moses Staff

Moses Staff has used batch scripts that can enable SMB on a compromised host.[41]

S0039 Net

Lateral movement can be done with Net through net use commands to connect to the on remote systems.[42]

S0056 Net Crawler

Net Crawler uses Windows admin shares to establish authenticated sessions to remote systems over SMB as part of lateral movement.[43]

S0368 NotPetya

NotPetya can use PsExec, which interacts with the ADMIN$ network share to execute commands on remote systems.[44][45][46]

S0365 Olympic Destroyer

Olympic Destroyer uses PsExec to interact with the ADMIN$ network share to execute commands on remote systems.[47][46]

C0014 Operation Wocao

During Operation Wocao, threat actors used Impacket's as well as accessing the C$ and IPC$ shares to move laterally.[48]

G0071 Orangeworm

Orangeworm has copied its backdoor across open network shares, including ADMIN$, C$WINDOWS, D$WINDOWS, and E$WINDOWS.[37]

S0029 PsExec

PsExec, a tool that has been used by adversaries, writes programs to the ADMIN$ network share to execute commands on remote systems.[46]

S0019 Regin

The Regin malware platform can use Windows admin shares to move laterally.[49]

S1073 Royal

Royal can use SMB to connect to move laterally.[50]

S0446 Ryuk

Ryuk has used the C$ network share for lateral movement.[51]

G0034 Sandworm Team

Sandworm Team has copied payloads to the ADMIN$ share of remote systems and run net use to connect to network shares.[4][52]

S0140 Shamoon

Shamoon accesses network share(s), enables share access to the target device, copies an executable payload to the target system, and uses a Scheduled Task/Job to execute the malware.[53]

C0024 SolarWinds Compromise

During the SolarWinds Compromise, APT29 used administrative accounts to connect over SMB to targeted users.[54]

S0603 Stuxnet

Stuxnet propagates to available network shares.[55]

G0028 Threat Group-1314

Threat Group-1314 actors mapped network drives using net use.[56]

G1022 ToddyCat

ToddyCat has used locally mounted network shares for lateral movement through targated environments.[57]

G0010 Turla

Turla used net use commands to connect to lateral systems within a network.[58]

G0102 Wizard Spider

Wizard Spider has used SMB to drop Cobalt Strike Beacon on a domain controller for lateral movement.[59][60]

S0672 Zox

Zox has the ability to use SMB for communication.[61]

S0350 zwShell

zwShell has been copied over network shares to move laterally.[62]


ID Mitigation Description
M1037 Filter Network Traffic

Consider using the host firewall to restrict file sharing communications such as SMB. [63]

M1035 Limit Access to Resource Over Network

Consider disabling Windows administrative shares.

M1027 Password Policies

Do not reuse local administrator account passwords across systems. Ensure password complexity and uniqueness such that the passwords cannot be cracked or guessed.

M1026 Privileged Account Management

Deny remote use of local admin credentials to log into systems. Do not allow domain user accounts to be in the local Administrators group multiple systems.


ID Data Source Data Component Detects
DS0017 Command Command Execution

Monitor executed commands and arguments that connect to remote shares, such as Net, on the command-line interface and Discovery techniques that could be used to find remotely accessible systems.[64]

Note: Event ID 4104 (from the Microsoft-Windows-Powershell/Operational log) captures Powershell script blocks, which can be analyzed and used to detect on potential connections and writing to remote shares.

DS0028 Logon Session Logon Session Creation

Monitor for logon behavior (ex: EID 4624 Logon Type 3) using Valid Accounts to interact with a remote network share using Server Message Block (SMB). The adversary may then perform actions as the logged-on user. Ensure that proper logging of accounts used to log into systems is turned on and centrally collected. Windows logging is able to collect success/failure for accounts that may be used to move laterally and can be collected using tools such as Windows Event Forwarding. [65][66]

DS0033 Network Share Network Share Access

Monitor interactions with network shares, such as reads or file transfers, using Server Message Block (SMB).

DS0029 Network Traffic Network Connection Creation

Monitor for newly constructed network connections (typically over ports 139 or 445), especially those that are sent or received by abnormal or untrusted hosts. Correlate these network connections with remote login events and associated SMB-related activity such as file transfers and remote process execution.

Note: Event ID is for Zeek but can also be implemented in other Network Analysis Frameworks by parsing & decoding captured SMB2 network traffic. Preference would be to detect smb2_write_response event (instead of smb2_write_request), because it would confirm the file was actually written to the remote destination. Unfortunately, Bro/Zeek does not have an event for that SMB message-type yet. From a network traffic capture standpoint, it’s important to capture the right traffic for this type of detection to function (e.g., all endpoint to endpoint if possible or workstation to server and workstation to workstation). As such, it is helpful to have a centralized server area where it is possible to monitor communications between servers and endpoints.

Analytic 1 and 2 are very similar, with the key difference being that Implementation 2 is intended to capture multiple attempts at lateral movement originating from the same host within a short time period (5 minutes).

  • smb2_write_request, smb1_write_andx_response is indication of an SMB file write to a Windows Admin File Share: ADMIN$ or C$

  • smb2_tree_connect_request, smb1_tree_connect_andx_request is observed originating from the same host, regardless of write-attempts and regardless of whether or not any connection is successful —just connection attempts— within a specified period of time (REPEATS 5 TIMES WITHIN 5 MINUTES FROM SAME src_ip).

From a network traffic capture standpoint, it’s important to capture the right traffic for this type of detection to function (e.g., all endpoint to endpoint if possible or workstation to server and workstation to workstation). As such, it is helpful to have a centralized server area where it is possible to monitor communications between servers and endpoints.The Service Control Manager (SCM) can be used to copy a file to the ADMIN$ share and execute it as a service. This can be detected by looking for incoming RPC network connections to the Service Control Manager, followed by services.exe spawning a child process.

Analytic 1 - Basicsource="*Zeek:SMB_Files" EventCode IN ("smb2_write_request", "smb1_write_andx_response", "smb2_tree_connect_request", "smb1_tree_connect_andx_request") AND (Path="ADMIN$" OR Path="C$")

Network Traffic Flow

Monitor network data for uncommon SMB data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Network Analysis frameworks such as Zeek can be used to capture, decode, and alert on SMB network flows.


  • The logic for Implementation 1 is based around detecting on SMB write requests, which are often used by adversaries to move laterally to another host. Unlike SMB Reads, SMB Write requests typically require an additional level of access, resulting in less activity. Focusing on SMB Write activity narrows the field to looking at techniques associated with actively changing remote hosts, instead of passively reading files.
  • The logic for Implementation 2 is based around detection of new processes that were created from a file written to an SMB share. First, a file is remotely written to a host via an SMB share; then, a variety of Execution techniques can be used to remotely establish execution of the file or script. To detect this behavior, look for files that are written to a host over SMB and then later run directly as a process or in the command line arguments. SMB File Writes and Remote Execution may happen normally in an environment, but the combination of the two behaviors is less frequent and more likely to indicate adversarial activity.

Analytic 1 - SMB Write

source="*Zeek:SMB_Files" port="445" AND protocol="smb.write"

DS0009 Process Process Creation

Monitor for the creation of WMI Win32_Process class and method Create to interact with a remote network share using Server Message Block (SMB). Relevant indicators detected by Bro/Zeek is IWbemServices::ExecMethod or IWbemServices::ExecMethodAsync. One thing to notice is that when the Create method is used on a remote system, the method is run under a host process named "Wmiprvse.exe".

The process WmiprvSE.exe is what spawns the process defined in the CommandLine parameter of the Create method. Therefore, the new process created remotely will have Wmiprvse.exe as a parent. WmiprvSE.exe is a DCOM server and it is spawned underneath the DCOM service host svchost.exe with the following parameters C:\WINDOWS\system32\svchost.exe -k DcomLaunch -p. From a logon session perspective, on the target, WmiprvSE.exe is spawned in a different logon session by the DCOM service host. However, whatever is executed by WmiprvSE.exe occurs on the new network type (3) logon session created by the user that authenticated from the network.

Analytic 1 - Basic

(source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode="1") OR (source="WinEventLog:Security" EventCode="4688") AND ParentImage="*wmiprvse.exe" AND TargetLogonID="0x3e7"


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