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Tuesday, April 11, 2017

Chronicles of a Threat Hunter: Hunting for Remotely Executed Code via Services & Lateral Movement with Sysmon, Win Event Logs, and ELK





One of the main reasons that encouraged me to start this series "Chronicles of a Threat Hunter" was the lack of detection techniques provided by security researchers after writing awesome pen-testing articles. Do NOT get me wrong, they do an EXCELLENT job describing tools and techniques used by real adversaries, but only a few share ways to detect or hunt for what they write about.

A few months ago, I read an article about moving laterally after compromising NT LAN Manager (NTLM) password hashes by leveraging PsExec-Style techniques. It was a great write-up, but It only provided information about the behavior of each tool at a high-level. You can read the article here

In this post, I will show you what the attack looks like from a hunter's perspective. One thing that I found very interesting in the implementation of this technique was the execution of code (Stager) remotely via services right after authenticating to the box establishing a session with their command and control which is exactly what I will focus on in this post.


Requirements:


  • Sysmon Installed (I have version 6 installed)
  • Winlogbeat forwarding logs to an ELK Server
  • I recommend to read my series "Setting up a Pentesting.. I mean, a Threat Hunting Lab" specifically part 5 & 6 to help you set up your environment if you haven't set up one yet.
  • Success audit events for File Share and Detail File Share set up. I will show you how if you dont know how to update/edit an Audit Policy. .
  • Metasploit's psexec Module
  • Invoke-SMBExec.ps1 from the Invoke-TheHash project by Kevin Robertson


Remotely Launched Executables via Services


There are several ways to cause code to execute on a remote host. One of the most common methods is via the Windows Service Control Manager (SCM), which allows authorized users to remotely create and modify services. Several tools, such as PsExec, use this functionality. When a client remotely communicates with the Service Control Manager, there are two observable behaviors. 
First, the client connects to the RPC Endpoint Mapper over 135/tcp. This handles authentication, and tells the client what port the endpoint—in this case the SCM—is listening on. Then, the client connects directly to the listening port on services.exe. If the request is to start an existing service with a known command line, the the SCM process will run the corresponding command.[Source]



CreateService Function


Creates a service object and adds it to the specified service controls manager database. A few parameters that will help you understand a few codes used during this exercise are: [Source]


ServiceType



Value
Meaning
SERVICE_ADAPTER
0x00000004
Reserved.
SERVICE_FILE_SYSTEM_DRIVER
0x00000002
File system driver service.
SERVICE_KERNEL_DRIVER
0x00000001
Driver service.
SERVICE_RECOGNIZER_DRIVER
0x00000008
Reserved.
SERVICE_WIN32_OWN_PROCESS
0x00000010
Service that runs in its own process.
SERVICE_WIN32_SHARE_PROCESS
0x00000020
Service that shares a process with one or more other services.
SERVICE_USER_OWN_PROCESS
0x00000050
The service runs in its own process under the logged-on user account.
SERVICE_USER_SHARE_PROCESS
0x00000060
The service shares a process with one or more other services that run under the logged-on user account.



StartType


The service start options.


Value
Meaning
SERVICE_AUTO_START
0x00000002
A service started automatically by the service control manager during system startup. For more information, see Automatically Starting Services.
SERVICE_BOOT_START
0x00000000
A device driver started by the system loader. This value is valid only for driver services.
SERVICE_DEMAND_START
0x00000003
A service started by the service control manager when a process calls the StartService function.
SERVICE_DISABLED
0x00000004
A service that cannot be started. Attempts to start the service result in the error code ERROR_SERVICE_DISABLED.
SERVICE_SYSTEM_START
0x00000001
A device driver started by the IoInitSystem function. This value is valid only for driver services.



ErrorControl


The severity of the error, and action taken, if this service fails to start.


Value
Meaning
SERVICE_ERROR_CRITICAL
0x00000003
The startup program logs the error in the event log, if possible. If the last-known-good configuration is being started, the startup operation fails. Otherwise, the system is restarted with the last-known good configuration.
SERVICE_ERROR_IGNORE
0x00000000
The startup program ignores the error and continues the startup operation.
SERVICE_ERROR_NORMAL
0x00000001
The startup program logs the error in the event log but continues the startup operation.
SERVICE_ERROR_SEVERE
0x00000002
The startup program logs the error in the event log. If the last-known-good configuration is being started, the startup operation continues. Otherwise, the system is restarted with the last-known-good configuration.





CreateService Remarks


The CreateService function creates a service object and installs it in the service control manager database by creating a key with the same name as the service under the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services

Information specified by CreateService, ChangeServiceConfig, and ChangeServiceConfig2 is saved as values under this key. The following are examples of values stored for a service.[Source]



Value
Description

DependOnGroup

Load-ordering groups on which this service depends, as specified by lpDependencies.


DependOnService

Services on which this service depends, as specified by lpDependencies.


Description


Description specified by ChangeServiceConfig2 .

DisplayName


Display name specified by lpDisplayName.

ErrorControl


Error control specified by dwErrorControl.

FailureActions


Failure actions specified by ChangeServiceConfig2 .

Group

Load ordering group specified by lpLoadOrderGroup. Note that setting this value can override the setting of the DependOnService value.


ImagePath


Name of binary file, as specified by lpBinaryPathName.

ObjectName


Account name specified by lpServiceStartName.

Start


When to start service, as specified by dwStartType.

Tag


Tag identifier specified by lpdwTagId.

Type


Service type specified by dwServiceType.









Getting ready for the hunt


Getting a Sysmon Config ready


I will use use my basic sysmon config StartLogging.xml that helps me to filter out most of the noise on an initial Sysmon setup. You might have to add some more exclusions to it depending on how your Windows system is set up. 





Download and save the Sysmon config in a preferred location of your choice. Then, update your Sysmon rules configuration. In order to do this, make sure you run cmd.exe as administrator, and update your Sysmon rules with the configuration you just downloaded by running the following commands:


Sysmon.exe -c [Sysmon config xml file]




Getting a Kibana dashboard ready


As you may already know about me, I prefer to look at all my logs in different visualizations under one dashboard in Kibana instead of using the event viewer console. It makes the analysis way easier allowing me to look at all the data at once and filter out noise. If you want to learn the basics of how to build a Kibana dashboard, you can read about it here and here. Create one similar to the one shown in figure 1 below.


Figure 1. Lateral Movement Dashboard.




On the same dashboard, I like to also have a saved search of all the events sent to my ELK Server. You can just add it at the bottom of the visualizations shown in figure 1 above. That helps me to visualize my events in a timeline style as shown in figure 2 below.


Figure 2. TimeLine style for Lateral Movement dashboard.




Update/Create an AD Global Audit Policy


For this exercise, we want to make sure that we have "File Share" audit events enabled. If you have a domain controller set up in your environment with AD services enabled, you can create Audit Policies and apply them to your whole domain. If you dont have a custom Audit Policy set up in your environment yet, you can follow one of my posts here starting on "Figure 59. Creating a new GPO" to help you create one. If you have one set up already, do the following:

  • Open Group Policy Management > right-click on your custom Global Auditing Policy > Click on Edit
    • It will open the Group Policy Management Editor
  • Expand Computer Configuration> Windows Settings > Security Settings > Advanced Audit Policy Configuration> Audit Policies > ObjectAccess
  • Once in ObjectAccess, right click on "Audit File Share" & "Audit Detailed File Share" and select "Configure the following audit events"
  • Select the checkbox next to Success and Apply.


Figure 3. Enabling Audit File Share success events.




Figure 4. Enabling Audit Detailed File Share success events.




Finally, make sure you refresh local and Active Directory-based Group Policy settings on your endpoints. Run the following command on your endpoints as shown in figure 5 below:

gpupdate /force


Figure 5. Updating GPOs on endpoints.




Delete/Clean your Index 


If you have read my previous posts, you should know that in order to reduce the number of logs before and during executing an attack, make sure you delete/clear your Index by running the following command as shown below:

curl -XDELETE 'localhost:9200/[name of your index]?pretty'

Do this in your ELK server a few seconds before you run your tools against your compromised computer.




Hunting for Metasploit PsExec Module


Attack Scenario


An adversary dumped hashes from a compromised system's SAM database and used the Administrator's hash with the metasploit's psexec module to move laterally in the network.



Running Metasploit's PsExec module


Make sure you clear/delete your index before running the module.


Figure 6. Setting up PsExec Module options before executing it.




Figure 7. Executing Metasploit's PsExec module.




First look at our Dashboard


Go to your dashboard right away and refresh it to show you what happened in the past 15-30 minutes. I filtered EID 7 events to have a cleaner timeline of events and focus on authentication logs, registry events, process execution, etc.


Figure 8. Lateral Movement Dashboard First Look.


I see a few interesting events:

  • Win EID 4624
    • Logon Type:  3 (Network)
    • Package Name : NTLM V2
    • Logon Process: NtLmSsp
    • Key Length: 0
  • Win 4672 Special Privileges assigned to new logon
  • Win 4776 Credentials Validation
  • Win 7045 A Service was installed in the system
  • Sysmon EID 1 Images
    • Services.exe
    • PowerShell.exe
  • Win EID 5140 & 5145 ShareNames
    • \\*\IPC$
    • \\*\ADMIN$
  • Workstation communications
    • P5MPJqc1EgXaOY1M ===> VA-WK-ACCT001.hf.com
    • Kali machine: P5MPJqc1EgXaOY1M
    • Target/Victim's Computer VA-WK-ACCT001.hf.com
  • Sysmon EID 13 & 12 : Registry Keys (look in page 1 & 2)
    • HKLM\System\CurrentControlSet\services\OzZkywlj
    • HKLM\System\CurrentControlSet\services\OzZkywlj\Start
    • HKLM\System\CurrentControlSet\services\OzZkywlj\DeleteFLag
    • HKLM\System\CurrentControlSet\services\OzZkywlj\DisplayName
    • HKLM\System\CurrentControlSet\services\OzZkywlj\ErrorControl
    • HKLM\System\CurrentControlSet\services\OzZkywlj\ImagePath
    • HKLM\System\CurrentControlSet\services\OzZkywlj\ObjectName
    • HKLM\System\CurrentControlSet\services\OzZkywlj\Type
  • Sysmon EID 13 & 12 Registry Events Details:
    • DWORD (0x00000000,0x00000001,0x00000003,0x00000004,0x00000010)
    • LocalSystem
    • CFvsCYjeuYHYlewh
  • Pipe Names
    • \srvsvc
    • \wkssvc
    • <Anonymous Pipes>
    • \ntsvcs




Events Timeline (I)


The first events are related to a successful authentication happening on the target machine and a new service being set up with specific properties.


Figure 9. First events.




Authentication Events (Pass-The-Hash Activity)


EID 4776 (Attempt to validate the credentials for an account) - 04/10/17 19:15:36.169

When a system successfully authenticates a local SAM account via NTLM (instead of Kerberos), the system logs this event. This specifies which user account was used to log on and the computer's name from which the user initiated the logon in the Workstation Field as shown in figure 10 below.


Figure 10. Attempt to validate the credentials for an account.




EID 4624 (An account was successfully logged on) - 04/10/17 19:15:36.169

An account successfully logged on from 172.18.39.101 (Kali) with an NTLM hash.


Figure 11. An account was successfully logged on.




EID 4672 (Special privileges assigned to new logon) - 04/10/17 19:15:36.169

This event lets you know whenever an account assigned any "administrator equivalent" user rights logs on.  For instance you will see event 4672 in close proximity to logon events (4624) for administrators since administrators have most of these admin-equivalent rights. [Source]. Remember that privileges such as SeTakeOwnership, SeDebug, and SeImpersonate are admin-equivalent.




File Share Activity (Is PowerShell installed?)


EID 5140 (A network share object was accessed) - 04/10/17 19:15:36.183

This log can tell us when a user accesses a network share, but it does not tell us the exact file that the user accessed in the share. So far, all I see is \??\C:\Windows.


Figure 12. A Network share object was accessed.




EID 5145 (Detailed File Share event) - 04/10/17 19:15:36.190

Tracking the specific file that a user is accessing on a file share is possible when you have the Detailed File Share audit policy enabled. Now you understand why we enabled this audit policy at the beginning.


Figure 13. Checking PowerShell.exe via ADMIN$




Why check for PowerShell.exe?

As you can see in figure 14 below, the metasploit's PsExec module has a function to check for the presence of PowerShell in the target system. This is because the module has the option to use the old school way of dropping an executable onto the victim if PowerShell is not installed.


Figure 14. PsExec module checking if PowerShell is installed or not in the victim's system.




Service Control Manager (SCM) Access


EID 18
 - 04/10/17 19:15:36.237

During system startup, a named pipe NTSVCS is created as a remote procedure call (RPC) interface between the SCM and the SCPs (Service Control Processes) that interact with specific services. This event 18 is logged when a connection to a pipe is established. Common behavior when a service is about to be installed, created or modified.


Figure 15. \ntsvcs pipe connected.




EID 4674 (An operation was attempted on a privileged object) - 04/10/17 19:15:36.279

This specific event is also known for when a service is about to get installed, started, stopped or modified. We can see that the account used for this is the compromised account used to pass the hash. 


Figure 16. Access to SC Manager Object.




Service Creation and Installation


EID 12 (Registry object added or deleted) - 04/10/17 19:15:36.352

In this specific event, a Key was created with a random name.


Figure 17. Creating a random key for the new service.




EID 13 ( Registry Value Set) - 04/10/17 19:15:36.353 - 04/10/17 19:15:36.354

As you could see in figure 9 above, a new service was set up with specific values. One of the values that stand out is the value set to the ImagePath property of the new service as shown in figure 18 below.

  • HKLM\System\CurrentControlSet\services\OzZkywlj\ErrorControl 
    • Details: DWORD (0x00000000)
    • Value: SERVICE_ERROR_IGNORE
  • HKLM\System\CurrentControlSet\services\OzZkywlj\Start
    • Details: DWORD (0x00000003)
    • Value: SERVICE_DEMAND_START
  • HKLM\System\CurrentControlSet\services\OzZkywlj\Type
    • Details: DWORD (0x00000010)
    • Value: SERVICE_WIN32_OWN_PROCESS
  • HKLM\System\CurrentControlSet\services\OzZkywlj\ImagePath
    • Details: %%COMSPEC%% /b /c start /b /min powershell.exe -nop [Truncated]
  • HKLM\System\CurrentControlSet\services\OzZkywlj\DisplayName
    • Details: CFvsCYJeuYHYlewh
  • HKLM\System\CurrentControlSet\services\OzZkywlj\ObjectName
    • Details: LocalSystem



Figure 18. Metasploit Stager set up as part of the ImagePath property of the new service.




EID 7045 (A service was installed in the system) - 04/10/17 19:15:36.354

A System log that also provides information about a new service installed in the endpoint. This is also captured by EID 4697 if configured or enabled by default.


Figure 19. A service was installed in the system.




Events Timeline (II)


Once the service is installed, it is executed and a connection is established with the Metasploit Server. Then, the registry key holding the new service is deleted.


Figure 20. Timeline of initial events. Part II.




Execution of New Service


EID 1 (Process Create) - 04/10/17 19:15:36.382 04/10/17 19:15:36.411

Once the service gets started, services.exe runs the code or script set up under the IpagePath property of the new service. In this case, services as a parent runs cmd.exe (%%COMSPEC%%) to execute the rest of the commands/script (Stager)

Figure 21. Services executing the script 




Powershell gets spawned by cmd.exe and the rest of the code gets executed to finally establish the connection back with the Metasploit server. As you can see in figure 22 below, the Integrity level of the process is SYSTEM due to the fact that services get started/executed with SYSTEM privileges.


Figure 22. Stager being executed by PowerShell.




Deletion of Reg Key (New Service)


EID 13 (Registry Value Set)  - 04/10/17 19:15:36.419

After executing the new service and running the metasploit stager from the ImagePath property of the service, the service is disabled and set to be deleted. 
  • HKLM\System\CurrentControlSet\services\OzZkywlj\Start
    • Details: DWORD (0x00000004)
    • Value: SERVICE_DISABLED
  • HKLM\System\CurrentControlSet\services\OzZkywlj\DeleteFlag
    • Details: DWORD (0x00000001)
    • Value: DELETE

Figure 23. Setting a DeleteFlag to the new service.




EID 12 (Registry object added or deleted)  - 04/10/17 19:15:36.440

After the DeleteFlag is set, the registry key is deleted by services.exe.


Figure 24. Deleting Service.




Summary of Chains of Events Observed


Time Bucket: All within 1 second. Events ordered following their respective timestamps.

Source
EventID
Field
Details
WinEvent
4776
PackageName
MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
WinEvent
4776
Logon Account/TargetUserName
Administrator
WinEvent
4624
Source Workstation/WorkstationName
P5MPJqc1EgXaOY1M
WinEvent
4624
LogonType
3
WinEvent
4624
WorkstationName
P5MPJqc1EgXaOY1M
WinEvent
4624
Source Network Address/IPAddress
NOT  (::1 OR Localhost)
WinEvent
4624
LogonProcessName
NtLmSsp
WinEvent
4624
LmPackageName
NTLM V2
WinEvent
4624
KeyLength
0
WinEvent
4672
SubjectUsername/ TargetUserName
Administrator
WinEvent
5140
SubjectUsername
Administrator
WinEvent
5140
ShareName
\\*\ADMIN$ OR \\*\C$
WinEvent
5140
Source Address/IPAddress
172.18.39.101
WinEvent
5145
RelativeTargetName
System32\WindowsPowerShell\v1.0\powershell.exe OR Windows\System32\WindowsPowerShell\v1.0\powershell.exe
WinEvent
5145
SubjectUsername
Administrator
WinEvent
5145
ShareName
\\*\ADMIN$ OR \\*\C$
WinEvent
5145
Source Address/IPAddress
172.18.39.101
Sysmon
18
PipeName
\ntsvcs
WinEvent
4674
ObjectServer
SC Manager
WinEvent
4674
ObjectType
SC_MANAGER OBJECT
WinEvent
4674
SubjectUsername
Administrator
Sysmon
12
EventType
CreateKey
Sysmon
12
Image
C:\Windows\system32\services.exe
Sysmon
12
TargetObject
HKLM\System\CurrentControlSet\services\OzZkywlj
Sysmon
13
Image
C:\Windows\system32\services.exe
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\OzZkywlj" AND (ErrorControl OR Start OR Type OR DisplayName OR ObjectName)
Sysmon
13
Details
("DWORD" AND (0x00000000 OR 0x00000003 OR 0x00000010)) AND CFvsCYJeuYHYlewh OR LocalSystem
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\OzZkywlj\ImagePath"
Sysmon
13
Details
%%COMSPEC%% OR cmd.exe OR powershell.exe OR Long Strings.
WinEvent
7045/4697
Service Name
CFvsCYJeuYHYlewh
WinEvent
7045/4607
Service File Name
%%COMSPEC%% OR cmd.exe OR powershell.exe OR Long Strings.
Sysmon
1
ParentImage
C:\Windows\system32\services.exe
Sysmon
1
Image
cmd.exe OR powershell.exe
Sysmon
13
Image
C:\Windows\system32\services.exe
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\OzZkywlj\" AND (Start OR DeleteFlag)
Sysmon
13
Details
"DWORD" AND (0x00000004 OR 0x00000001)
Sysmon
12
Image
C:\Windows\system32\services.exe
Sysmon
12
EventType
DeleteKey
Sysmon
12
TargetObject
"HKLM\System\CurrentControlSet\services\OzZkywlj"




RT: "Great, all I have to do is use another tool for lateral movement!"


I hear that all the time, and believe me, we (hunters) also have common sense :) and think about you using another tool, renaming processes or running things in memory. I am not trying to come up with a signature for an specific tool; Instead, I am trying to focus on the patterns of behavior of this technique used to move laterally. Let's say you want to use Invoke-SMBExec.ps1 from the Invoke-TheHash project by Kevin Robertson. What does it look like?




Hunting for Invoke-SMBExec (Invoke-TheHash)


Running Invoke-SMBExec


Make sure you clear/delete your index before running the module.


Figure 25. Running Invoke-SMBExec.




Figure 26. Established session with Empire.




Let's take a look at our Dashboard


Go to your dashboard, and refresh it to show you what happened in the past 15-30 minutes. I filtered EID 7 to not look at the images loaded on the systems allowing me to have a cleaner timeline of events and focus on authentication logs, registry events, etc.

Doesn't it look familiar?


Figure 27. Looking at Invoke-SMBExec activity.




A few events


EID 4624 - (Pass The hash activity) - 04/11/17 - 01:22:37.725


Figure 28. Pass The hash log.




EID 13 -  (ImagePath Property) - 04/11/17 - 05:22:38.322


Figure 29. Creation of malicious service. Set to execute Empire Stager.




EID 7045 (Service Installed on System) - 04/11/17 - 01:22:38.322


Figure 30. New Service Installed




EID 1 (Execution of Stager by Services.exe) - 04/11/17 - 05:22:38.483


Figure 31. Execution of Stager.




Figure 32. Execution of Stager




EID 12 (Deletion of Registry key/New Service) - 04/11/17 - 05:23:08.677


Figure 33. Deletion of registry key.





Summary of Chains of Events Observed (Pattern Approach)


Time Bucket: All within 1-2 seconds

I was able to get almost every single event that occurred after executing the Metasploit PsExec module (PowerShell Version) before. Below, you will see a summary of events, but showing the basic pattern of the tools tested in this post (Metasploit PsExec module & Invoke-SMBExec)


Source
EventID
Field
Details
WinEvent
4624
PackageName
MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
WinEvent
4624/4672
Logon Account/TargetUserName
Administrator
WinEvent
4624
Source Workstation/WorkstationName
Other Workstations
WinEvent
4624
LogonType
3
WinEvent
4624
WorkstationName
Other Workstations
WinEvent
4624
Source Network Address/IPAddress
NOT  (::1 OR Localhost)
WinEvent
4624
LogonProcessName
NtLmSsp
WinEvent
4624
LmPackageName
NTLM V2
WinEvent
4624
KeyLength
0
WinEvent
5140
SubjectUsername
NOT a ComputerName$
WinEvent
5140
ShareName
\\*\IPC$ OR \\*\ADMIN$ OR \\*\C$
WinEvent
5140
Source Address/IPAddress
NOT ( ::1 OR Localhost)
WinEvent
5145
RelativeTargetName
svcctl OR .exe OR Outlier
WinEvent
5145
SubjectUsername
NOT a ComputerName$
WinEvent
5145
ShareName
\\*\IPC$ OR \\*\ADMIN$ OR \\*\C$
WinEvent
5145
Source Address/IPAddress
NOT ( ::1 OR Localhost)
Sysmon
18
PipeName
\ntsvcs
Sysmon
12
EventType
CreateKey
Sysmon
12
Image
C:\Windows\system32\services.exe
Sysmon
12
TargetObject
HKLM\System\CurrentControlSet\services\[New Service]
Sysmon
13
Image
C:\Windows\system32\services.exe
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\" AND (ErrorControl OR Start OR Type OR DisplayName OR ObjectName)
Sysmon
13
Details
("DWORD" AND (0x00000000 OR 0x00000003 OR 0x00000010)) OR Random Service Name OR LocalSystem
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\" AND "ImagePath"
Sysmon
13
Details
%%COMSPEC%% OR cmd.exe OR powershell.exe OR Long Strings.
WinEvent
7045/4697
Service Name
Suspicious Name / Random
WinEvent
7045/4697
Service File Name
%%COMSPEC%% OR cmd.exe OR powershell.exe OR Long Strings.
Sysmon
1
ParentImage
C:\Windows\system32\services.exe
Sysmon
1
Image
cmd.exe OR powershell.exe
Sysmon
13
Image
C:\Windows\system32\services.exe
Sysmon
13
TargetObject
"HKLM\System\CurrentControlSet\services\" AND (Start OR DeleteFlag)
Sysmon
13
Details
"DWORD" AND (0x00000004 OR 0x00000001)
Sysmon
12
Image
C:\Windows\system32\services.exe
Sysmon
12
EventType
DeleteKey
Sysmon
12
TargetObject
"HKLM\System\CurrentControlSet\services\[Random Name]"




Final Thoughts


It was a very interesting exercise to go deeper into the functionality of the two tools I tested in this post, and it was even more interesting to capture their patterns of behaviors when remotely executing code via services to move laterally.

We could use the the chains of events observed on both scenarios and come up with a pattern that could allow us to reduce the number of false positives when hunting for this specific lateral movement technique. 

We could create a basic logic with a few events:

EID 4624 + (EID 13 AND ("HKLM\System\CurrentControlSet\services\" AND "ImagePath" AND Details: (Long strings OR Base64 OR Suspicious Commands)) + (EID 7045/4697 AND ServiceFileName:(Long strings OR Base64 OR Suspicious Commands)) + (EID 1 AND ParentImage:services.exe AND CommandLine:(Long strings OR Base64 OR Suspicious Commands)) + (EID 12 AND EventType:"DeleteKey" AND TargetObject:""HKLM\System\CurrentControlSet\services\ [RandomName]") within a bucket time of 1-2 seconds.



A quick WIN?


I got you, why dont you look for the following?

event_id:13 AND Image:services.exe AND TargetObject: ("HKLM\\System\\CurrentControlSet\\services\\" AND "ImagePath" ) AND Details: /.{50,}/

that should give you long strings (unusual behavior) being set as values of ImagePath parameters of new or current services. That should annoy your RT :) (CobalStrike, Metasploit, Invoke-SMBExec, and potentially other tools leveraging this technique)



Hunting Techniques recommended


Grouping [Source]

"Grouping consists of taking a set of multiple unique artifacts and identifying when multiple of them appear together based on certain criteria. The major difference between grouping and clustering is that in grouping your input is an explicit set of items that are each already of interest. Discovered groups within these items of interest may potentially represent a tool or a TTP that an attacker might be using. An important aspect of using this technique consists of determining the specific criteria used to group the items, such as events having occurred during a specific time window.This technique works best when you are hunting for multiple, related instances of unique artifacts, such as the case of isolating specific reconnaissance commands that were executed within a specific timeframe."


Searching [Source]

The simplest method of hunting, searching is querying data for specific artifacts and can be performed in most tools. Unfortunately it may not always be the most effective method because it cannot produce outliers in the result set; you get exactly the results you searched for.Searching also requires a finely defined search criteria to prevent result overload. A search that is too broad will often flood an analyst with too many results to realistically process.



The ThreatHunter-Playbook


I have started to post all my findings into A ThreatHunter-Playbook. I started this project with other hunters in the industry to share knowledge and aid the development of techniques and hypothesis for hunting campaigns.

Project Github Link: https://github.com/Cyb3rWard0g/ThreatHunter-Playbook

Join the team and share what works for you!



Feedback is greatly appreciated! Thank you.



5 comments:

  1. Hi Roberto - Do you focus on Windows security for now? where did you pick up the skills for Python and Powershell? Which one do you like? if you have to master one over the other which one will you choose? Keep up the good work.

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  2. Hey Rajganesh, Thank you for the feedback. I am focusing on Windows for now. I will start working on MAC use cases soon and expand the scope of hunting in the ThreatHunter-Playbook repo. Regarding Python and PowerShell, I started using it more with the pentesteracademy.com videos. They were great resources that pushed me to read and do more research about it. I also read the Black Hat python book from Justin Seitz and the Windows PowerShell CookBook from Lee Holmes. I am using PowerShell more than Python. I think that both languages are geat, but I prefer to use PowerShell (Master it). I just recently started working with C# scripts so I would highly recommend to also look into that. Thank you again Raj, and I am glad you found the articles helpful. I hope you have a great weekend.

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  3. You are doing an amazing job. Exactly what I wanted to do, but better :). Anyway thanks for quick response. When you say C# scripts, what do you mean? Will you be posting on that?

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    1. I really appreciate it man! It would be great to look at some of the attacks that you are also blogging about and work on finding the pattern of similar techniques. Are you planning on adding detection/hunting techniques to your future posts? If so, let me know if you would like to collaborate with the https://github.com/Cyb3rWard0g/ThreatHunter-Playbook . Let me know what you think about it. Regarding C#, I just started to build some of the things that I had developed in PowerShell in C# (Offensive tools / basic scripts) since PowerShell logging and security controls are getting better and better. I want to document their footprint on my endpoints.

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  4. Yes, I definitely like to collaborate and possibly involved in some of your project. Let's discuss in couple of weeks. Have a great weekend!

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