securing windows with group policy

Josh rickard

 

 

7 yrs in IT

 

GCWN

GCFA

 

Windows Security

Digital Forensics

PowerShell Automation

 

LSD OU

Local

Local group policy

 

Machine/User specific settings

Free-for-all

Unmanaged

site

site based group policy

 

Location based

Subnet based

 

Domain

Domain

Organizational unit

your street

your home

your rooms

 

Even down to your refrigerator

manage users

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Restricted groups

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user rights

buying a new home

PRIVILEGES

  • Act As Part of the Operating System

  • Create a Token Object

  • Debug Programs

  • Impersonate a Client After Authentication

  • Load and Unload Device Drivers

  • Restore Files and Directories

  • Take Ownership

Impersonate A Client Privilege

  • Primary Security Access Token (SAT)
    • Impersonate a user’s SAT for other running processes
  • Used by network services to impersonate clients
  • Token stealing
    • Steal SATs for network authentication

 

SeImpersonatePrivilege

SeCreateGlobalPrivilege

Debug Programs Privilege

  • Grants read/write access to user & kernel-mode memory

  • Malware uses it for:

    • New thread injected into any process

    • Passwords, hashes, encryption keys and other data can be read out of kernel space memory without DLL injection.

  • Pass-The-Hash Attacks

    • Once malware has your password hash they can:

      • Extract password hashes of local accounts

      • Extract password hashes of interactive users with AD accounts

      • Plus others

SeDebugPrivilege

PETyA

LOgon rights

  • Deny access to this computer from the network
  • Deny log on as a batch job
  • Deny log on locally
  • Deny log on as a service
  • Deny log on through Remote Desktop Services
  • Allow log on through Remote Desktop Services

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Task scheduler

LEAST to MOST

  • Local Service

  • Virtual Service Account

  • Network Service

  • Local User Account (non-Admin)

  • Group Managed Service Account (domain user)

  • Domain User

  • Local System

  • Local User (local admin)

  • Global User (local admin

  • Global User (domain admin)

  • Global User (Enterprise Admin)

IMMEDIATE SCHEDULED TASKS

  • Program/Script:
    • C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
  • Add Arguments:
    • -NoProfile -Executionpolicy bypass -file "\\path\to\Invoke-Awesomeness.ps1" -Parameter 'MSPaint'

secure code execution

  • Run whether user is logged on or not
  • Do not store password
  • Run with highest privileges

Hint: If you are attempting to communicate over the network, try Network Service first!

manage services

iis server

  • DCOM Server Process Launcher
  • Event Log
  • Protected Storage
  • Remote Procedure Call (RPC) Service
  • Windows Installer
  • Windows NTLM Security Support Provider
  • Windows Process Activation Service
  • World Wide Web Publishing Service

TURN THEM OFF

process mitigation

DEP: Data Execution Prevention

 

SEHOP: Structured Exception Handler Overwrite Protection

 

ASLR: Address Space Layout Randomization

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scripting

Powershell

  • Enable ALL THE logging
  • Lockdown which IPs can use WMI
  • Digitally Sign your scripts
  • Use Immediate Scheduled Tasks

 

IF YOU CAN:

  • Use JEA (Just Enough Administration)
  • Use AppLocker (ContrainedLanguage Mode)

powershell lockdown policy

applocker

not so scary

EXEs, DLLs, Scripts, MSIs, APPXs

 

 

Three different conditions can be use

  • Hash Condition Rules
  • Path Condition Rules
  • Publisher Condition Rules

 

 

 

BLOCK rules always trump ALLOW rules

HAsh condition

  • Every file has a unique hash value

  • Positive

    • Unique hash for every executable

    • Secure!

  • Negative

    • Every update has a new hash

PATH CONDITION

  • Positive
    • Select an entire suite of products
    • You can use wildcards (*)
  • Negative
    • You must know all paths the application uses
    • C:\ProgramData
    • C:\Users\username\AppData\Local\*\*.zip\*

Publisher condition

  • Positive
    • Select an entire path to allow a suite of applications
    • You can use wildcards (*)
  • Negative
    • Only works for applications that are digitally signed

thank you

contact

email:    rickardja@live.com

blog:      https://msadministrator.com

twitter: @MS_dministrator

github:  https://github.com/MSAdministrator

 

slides: 

https://msadministrator.github.io/presentations/securing-windows-with-group-policy.html