<#
=============================================================================================
Name:           Audit SharePoint Online group membership changes report
Website:        o365reports.com

Script Highlights: 
~~~~~~~~~~~~~~~~~
1.The script uses modern authentication to connect to Exchange Online.   
2.The script can be executed with an MFA-enabled account too.   
3.Exports report results to CSV file.   
4.Helps to identify newly added and removed guest accounts separately. 
5.Allows you to generate an SPO group membership audit report for a custom period.   
6.Allows you to audit the group permission changes based on the workload, such as SharePoint and OneDrive. 
7.Automatically installs the EXO V2 module (if not installed already) upon your confirmation.  
8.The script is scheduler-friendly. I.e., Credentials can be passed as a parameter instead of getting interactively.

For detailed script execution:  https://o365reports.com/2022/06/22/audit-sharepoint-online-group-membership-changes-using-powershell
============================================================================================
#>

Param
(
    [Parameter(Mandatory = $false)]
    [Nullable[DateTime]]$StartDate,
    [Nullable[DateTime]]$EndDate,
    [switch]$SharePointOnly,
    [switch]$OneDriveOnly,
    [switch]$GuestOnly,
    [string]$UserName,
    [string]$Password
)

Function Connect_Exo
{
 #Check for EXO v2 module inatallation
 $Module = Get-Module ExchangeOnlineManagement -ListAvailable
 if($Module.count -eq 0) 
 { 
  Write-Host Exchange Online PowerShell V2 module is not available  -ForegroundColor yellow  
  $Confirm= Read-Host Are you sure you want to install module? [Y] Yes [N] No 
  if($Confirm -match "[yY]") 
  { 
   Write-host "Installing Exchange Online PowerShell module"
   Install-Module ExchangeOnlineManagement -Repository PSGallery -AllowClobber -Force
   Import-Module ExchangeOnlineManagement
  } 
  else 
  { 
   Write-Host EXO V2 module is required to connect Exchange Online.Please install module using Install-Module ExchangeOnlineManagement cmdlet. 
   Exit
  }
 } 
 Write-Host Connecting to Exchange Online...
 #Storing credential in script for scheduling purpose/ Passing credential as parameter - Authentication using non-MFA account
 if(($UserName -ne "") -and ($Password -ne ""))
 {
  $SecuredPassword = ConvertTo-SecureString -AsPlainText $Password -Force
  $Credential  = New-Object System.Management.Automation.PSCredential $UserName,$SecuredPassword
  Connect-ExchangeOnline -Credential $Credential
 }
 else
 {
  Connect-ExchangeOnline
 }
}

$MaxStartDate=((Get-Date).AddDays(-89)).Date

#Audit SharePoint group membership changes for past 90 days
if(($StartDate -eq $null) -and ($EndDate -eq $null))
{
 $EndDate=(Get-Date).Date
 $StartDate=$MaxStartDate
}
#Getting start date to audit SharePoint group membership changes report
While($true)
{
 if ($StartDate -eq $null)
 {
  $StartDate=Read-Host Enter start time for report generation '(Eg:04/28/2021)'
 }
 Try
 {
  $Date=[DateTime]$StartDate
  if($Date -ge $MaxStartDate)
  { 
   break
  }
  else
  {
   Write-Host `nAudit can be retrieved only for past 90 days. Please select a date after $MaxStartDate -ForegroundColor Red
   return
  }
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}


#Getting end date to audit SPO group membership changes report
While($true)
{
 if ($EndDate -eq $null)
 {
  $EndDate=Read-Host Enter End time for report generation '(Eg: 04/28/2021)'
 }
 Try
 {
  $Date=[DateTime]$EndDate
  if($EndDate -lt ($StartDate))
  {
   Write-Host End time should be later than start time -ForegroundColor Red
   return
  }
  break
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}

$OutputCSV=".\AuditSPOGrpMembershipChanges_$((Get-Date -format yyyy-MMM-dd-ddd` hh-mm` tt).ToString()).csv" 
$IntervalTimeInMinutes=1440    #$IntervalTimeInMinutes=Read-Host Enter interval time period '(in minutes)'
$CurrentStart=$StartDate
$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)

#Check whether CurrentEnd exceeds EndDate
if($CurrentEnd -gt $EndDate)
{
 $CurrentEnd=$EndDate
}

if($CurrentStart -eq $CurrentEnd)
{
 Write-Host Start and end time are same.Please enter different time range -ForegroundColor Red
 Exit
}

Connect_EXO
$CurrentResultCount=0
$AggregateResultCount=0
Write-Host `nAuditing SharePoint group membership changes from $StartDate to $EndDate...
$ProcessedAuditCount=0
$OutputEvents=0
$ExportResult=""   
$ExportResults=@()  


while($true)
{
 #Getting audit data for the given time range
 Search-UnifiedAuditLog -StartDate $CurrentStart -EndDate $CurrentEnd -Operations "AddedtoGroup,RemovedfromGroup" -SessionId s -SessionCommand ReturnLargeSet -ResultSize 5000 | ForEach-Object {
  $ResultCount++
  $ProcessedAuditCount++
  Write-Progress -Activity "`n     Retrieving SharePoint Group membership changes audit from $CurrentStart to $CurrentEnd.."`n" Processed audit record count: $ProcessedAuditCount"
  $MoreInfo=$_.auditdata
  $Operation=$_.Operations
  $User=$_.UserIds
  $PrintFlag="True"
  $AuditData=$_.auditdata | ConvertFrom-Json
  $SiteUrl=$AuditData.SiteUrl
  $MemberName=$AuditData.TargetUserorGroupName
  $MemberType=$AuditData.TargetUserorGroupType
  $Html=$AuditData.EventData
  $Group = [Regex]::new("(?<=Group>)(.*)(?=</Group>)")
  $AllowShare=[Regex]::new("(?<=ShareApplied>)(.*)(?=</MembersCan)")
  $MembersCanShare=$AllowShare.Match($Html).Value
  if($MembersCanShare -eq "")
  {$MembersCanShare="-"}
  $GroupName = $Group.Match($html).Value  
  $Result=$AuditData.ResultStatus
  $Workload=$AuditData.Workload

  #Filter result based on Workload
  if(($SharePointOnly.IsPresent) -and ($Workload -eq "OneDrive"))
  {
   $PrintFlag="False"
  }
  elseif(($OneDriveOnly.IsPresent) -and ($Workload -eq "SharePoint"))
  {
   $PrintFlag="False"
  }

  #Filter Guest users alone
  if(($GuestOnly.IsPresent) -and ($MemberType -ne "Guest"))
  {
   $PrintFlag="False"
  }  
 
  $EventTime=(Get-Date($AuditData.CreationTime)).ToLocalTime()  #Get-Date($AuditData.CreationTime) Uncomment to view the Activity Time in UTC
  #Export result to csv
  if($PrintFlag -eq "True")
  {
   $OutputEvents++
   $ExportResult=@{'Event Time'=$EventTime;'Performed By'=$User; 'Operation'=$Operation;'Site URL'=$SiteUrl;'Member Name'=$MemberName;'Member Type'=$MemberType;'Workload'=$Workload;'Group Name'=$GroupName;'Members Can Share Sites&Files'=$MembersCanShare;'More Info'=$MoreInfo}
   $ExportResults= New-Object PSObject -Property $ExportResult  
   $ExportResults | Select-Object 'Event Time','Performed By','Operation','Group Name','Member Name','Member Type','Members Can Share Sites&Files','Site URL','Workload','More Info' | Export-Csv -Path $OutputCSV -Notype -Append 
  }
 }
 $currentResultCount=$currentResultCount+$ResultCount
 
 if($CurrentResultCount -ge 50000)
 {
  Write-Host Retrieved max record for current range.Proceeding further may cause data loss or rerun the script with reduced time interval. -ForegroundColor Red
  $Confirm=Read-Host `nAre you sure you want to continue? [Y] Yes [N] No
  if($Confirm -match "[Y]")
  {
   Write-Host Proceeding audit log collection with data loss
   [DateTime]$CurrentStart=$CurrentEnd
   [DateTime]$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
   $CurrentResultCount=0
   if($CurrentEnd -gt $EndDate)
   {
    $CurrentEnd=$EndDate
   }
  }
  else
  {
   Write-Host Please rerun the script with reduced time interval -ForegroundColor Red
   Exit
  }
 }

 
 if($ResultCount -lt 5000)
 { 
  if($CurrentEnd -eq $EndDate)
  {
   break
  }
  $CurrentStart=$CurrentEnd 
  if($CurrentStart -gt (Get-Date))
  {
   break
  }
  $CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
  $CurrentResultCount=0
  if($CurrentEnd -gt $EndDate)
  {
   $CurrentEnd=$EndDate
  }
 }                                                                                             
 $ResultCount=0
}

#Open output file after execution
If($OutputEvents -eq 0)
{
 Write-Host No records found
}
else
{
 Write-Host `nThe output file contains $OutputEvents audit records
 if((Test-Path -Path $OutputCSV) -eq "True") 
 {
  Write-Host `n "The Output file available in:" -NoNewline -ForegroundColor Yellow; Write-Host "$OutputCSV"`n
  $Prompt = New-Object -ComObject wscript.shell   
  $UserInput = $Prompt.popup("Do you want to open output file?",`   
 0,"Open Output File",4)   
  If ($UserInput -eq 6)   
  {   
   Invoke-Item "$OutputCSV"     
  } 
 Write-Host `n~~ Script prepared by AdminDroid Community ~~`n -ForegroundColor Green
 Write-Host "~~ Check out " -NoNewline -ForegroundColor Green; Write-Host "admindroid.com" -ForegroundColor Yellow -NoNewline; Write-Host " to get access to 1800+ Microsoft 365 reports. ~~" -ForegroundColor Green `n`n
 }
}

#Disconnect Exchange Online session
Disconnect-ExchangeOnline -Confirm:$false -InformationAction Ignore -ErrorAction SilentlyContinue