In the ever-evolving landscape of IT, monitoring and analyzing event logs is crucial for maintaining system health, diagnosing issues, and ensuring security compliance.
Event logs provide a rich source of information about the state and behavior of systems, and being able to efficiently search and filter these logs can significantly enhance an IT professional’s ability to manage their infrastructure.
This post delves into a PowerShell script that simplifies the process of searching event logs, making it easier to pinpoint specific events based on criteria such as event log name, source, event ID, and more.
The Significance of Event Log Management in IT
Event logs are records of system, security, and application events on a computer. These logs are indispensable for troubleshooting issues, auditing security incidents, and ensuring compliance with regulatory standards.
For Managed Service Providers (MSPs) and IT professionals, the ability to quickly and accurately search through these logs is vital. Without efficient tools, this task can become cumbersome, especially when dealing with a large number of systems or complex environments.
PowerShell, a powerful scripting language developed by Microsoft, offers robust capabilities for interacting with event logs. The script we’re discussing today is designed to streamline the search process, enabling IT professionals to quickly locate relevant events within the Event Viewer.
The Script:
#Requires -Version 5.1
<#
.SYNOPSIS
Search for specific events in Event Viewer based on the event log they were in, the source of the event, or the specific event IDs used. One of these three options is required for the search.
.DESCRIPTION
Search for specific events in Event Viewer based on the event log they were in, the source of the event, or the specific event IDs used. One of these three options is required for the search.
.EXAMPLE
-EventLogName "Application"
Matching Events Found!
LogName : Application
ProviderName : Microsoft-Windows-Security-SPP
Id : 16384
TimeCreated : 4/4/2024 10:00:48 AM
Message : Successfully scheduled Software Protection service for re-start at 2024-04-04T21:19:48Z. Reason: Rul...
LogName : Application
ProviderName : Microsoft-Windows-Security-SPP
Id : 16394
TimeCreated : 4/4/2024 10:00:17 AM
Message : Offline downlevel migration succeeded.
LogName : Application
ProviderName : Microsoft-Windows-Security-SPP
Id : 16384
TimeCreated : 4/4/2024 9:59:59 AM
Message : Successfully scheduled Software Protection service for re-start at 2024-04-04T21:19:59Z. Reason: Rul...
PARAMETER: -EventLogName "Application"
Specify the name of the Event Log from which to retrieve events.
PARAMETER: -EventLogSource "Microsoft-Windows-Kernel-General"
Determines the source of the events to retrieve.
PARAMETER: -EventLogMessage "Alert"
Filters events by the text contained in the event's message.
PARAMETER: -EventIDs "12, 13, 6008"
A comma-separated list of event IDs to include in the search.
PARAMETER: -excludeEventIDs "13"
A comma-separated list of event IDs to exclude from the search.
PARAMETER: -StartDate "12/24/2021"
Defines the start date and time for the event search. Events logged before this time will not be included in the results.
PARAMETER: -EndDate "12/29/2021"
Sets the end date and time for the event search. Events logged after this time will not be included.
PARAMETER: -MultilineCustomField "replaceMeWithAcustomFieldName"
Specify the name of a multiline custom field to optionally store the search results in. Leave blank to not set a multiline field.
PARAMETER: -WysiwygCustomField "replaceMeWithACustomFieldName"
Specify the name of a WYSIWYG custom field to optionally store the search results in. Leave blank to not set a WYSIWYG field.
.NOTES
Minimum OS Architecture Supported: Windows 10, Windows Server 2016
Release Notes: Initial Release
By using this script, you indicate your acceptance of the following legal terms as well as our Terms of Use at https://www.ninjaone.com/terms-of-use.
Ownership Rights: NinjaOne owns and will continue to own all right, title, and interest in and to the script (including the copyright). NinjaOne is giving you a limited license to use the script in accordance with these legal terms.
Use Limitation: You may only use the script for your legitimate personal or internal business purposes, and you may not share the script with another party.
Republication Prohibition: Under no circumstances are you permitted to re-publish the script in any script library or website belonging to or under the control of any other software provider.
Warranty Disclaimer: The script is provided “as is” and “as available”, without warranty of any kind. NinjaOne makes no promise or guarantee that the script will be free from defects or that it will meet your specific needs or expectations.
Assumption of Risk: Your use of the script is at your own risk. You acknowledge that there are certain inherent risks in using the script, and you understand and assume each of those risks.
Waiver and Release: You will not hold NinjaOne responsible for any adverse or unintended consequences resulting from your use of the script, and you waive any legal or equitable rights or remedies you may have against NinjaOne relating to your use of the script.
EULA: If you are a NinjaOne customer, your use of the script is subject to the End User License Agreement applicable to you (EULA).
#>
[CmdletBinding()]
param (
[Parameter()]
[String]$EventLogName,
[Parameter()]
[String]$EventLogSource,
[Parameter()]
[String]$EventLogMessage,
[Parameter()]
[String]$EventIDs,
[Parameter()]
[String]$ExcludeEventIDs,
[Parameter()]
[datetime]$StartDate,
[Parameter()]
[datetime]$EndDate,
[Parameter()]
[String]$MultilineCustomField,
[Parameter()]
[String]$WysiwygCustomField
)
begin {
# Set parameters using dynamic script variables.
if ($env:eventLogName -and $env:eventLogName -notlike "null") { $EventLogName = $env:eventLogName }
if ($env:eventLogSource -and $env:eventLogSource -notlike "null") { $EventLogSource = $env:eventLogSource }
if ($env:eventLogMessage -and $env:eventLogMessage -notlike "null") { $EventLogMessage = $env:eventLogMessage }
if ($env:eventIds -and $env:eventIds -notlike "null") { $EventIDs = $env:eventIds }
if ($env:excludeEventIds -and $env:excludeEventIds -notlike "null") { $ExcludeEventIDs = $env:excludeEventIds }
if ($env:eventStart -and $env:eventStart -notlike "null") { $StartDate = $env:eventStart }
if ($env:eventEnd -and $env:eventEnd -notlike "null") { $EndDate = $env:eventEnd }
if ($env:multilineCustomFieldName -and $env:multilineCustomFieldName -notlike "null") { $MultilineCustomField = $env:multilineCustomFieldName }
if ($env:wysiwygCustomFieldName -and $env:wysiwygCustomFieldName -notlike "null") { $WysiwygCustomField = $env:wysiwygCustomFieldName }
# Check if both StartDate and EndDate are provided and if StartDate is earlier than EndDate
if (($StartDate -and $EndDate) -and $StartDate -gt $EndDate) {
Write-Host -Object "[Error] Start date cannot be earlier than end date!"
exit 1
}
# Verify that WysiwygField and MultiLineField are not the same, exiting with an error if they are.
if ($WysiwygCustomField -and $MultilineCustomField -and ($WysiwygCustomField -eq $MultilineCustomField)) {
Write-Host -Object "[Error] Wysiwyg Field and Multiline Field are the same! Custom fields cannot be the same type."
Write-Host -Object "https://ninjarmm.zendesk.com/hc/en-us/articles/18601842971789-Custom-Fields-by-Type-and-Functionality"
exit 1
}
# Ensure that at least one of Event ID, Event Log Name, or Event Source is provided for the query
if (!$EventIDs -and !$EventLogName -and !$EventLogSource) {
Write-Host -Object "[Error] You must provide either an Event ID, Event Log Name or Event Source."
exit 1
}
# Trimming trailing spaces.
if ($EventLogName) {
$EventLogName = $EventLogName.Trim()
}
# Retrieve and sort all event log names available on the system
$EventLogNamesOnSystem = Get-WinEvent -ListLog * -ErrorAction SilentlyContinue | Sort-Object LogName
# Check if the provided EventLogName exists in the system's event logs
if ($EventLogName -and ($EventLogNamesOnSystem).LogName -notcontains $EventLogName) {
# If not found, print an error message and a list of valid event log names, then exit the script
Write-Host -Object "[Error] Event Log '$EventLogName' doesn't exist! See the list below for valid event log names."
Write-Host -Object "### Valid Event Log Names ###"
$EventLogNamesOnSystem | Select-Object -ExpandProperty LogName | Write-Host
exit 1
}
$InvalidEventSourceCharacters = "[\\/<>&`"%\|']"
if ($EventLogSource) {
if ($EventLogSource -match $InvalidEventSourceCharacters) {
Write-Host -Object "[Error] Event Log Source '$EventLogSource' contains an invalid character!"
exit 1
}
if ($EventLogSource.Length -gt 255) {
Write-Host -Object "[Error] Event Log Source '$EventLogSource' is too large to be an event source!"
exit 1
}
# Trims the event log source for trailing spaces
$EventLogSource = $EventLogSource.Trim()
}
# Prepare a list to hold valid event IDs to search for
$EventIdsToSearch = New-Object System.Collections.Generic.List[int]
# Process the input event IDs, removing any that are not purely numerical
if ($EventIDs -and $EventIDs -match ",") {
# If multiple event IDs are provided and separated by commas, split them
$EventIDs -split "," | ForEach-Object {
$EventId = $_.Trim()
# Validate each event ID to ensure it's numerical
if ($EventId -match '[a-zA-Z]|\W') {
# If not, print an error and skip adding this ID to the list
Write-Host "[Error] Event ID '$EventId' is not a valid event id. Removing it from the search."
$ExitCode = 1
return
}
# Check size of event id
if ([long]$EventId -gt 65535 -or [long]$EventId -lt 0) {
Write-Host "[Error] Event ID '$EventId' is not a valid event id. Event ID's must be less than or equal to 65535 and greater than or equal to 0. Removing it from the search."
$ExitCode = 1
return
}
# Add the validated event ID to the list
$EventIdsToSearch.Add($EventId)
}
}
elseif ($EventIDs) {
$EventId = $EventIDs.Trim()
# Handle a single event ID input
if ($EventId -match '[a-zA-Z]|\W') {
Write-Host "[Error] Event ID '$EventId' is not a valid event id. Removing it from the search."
$ExitCode = 1
}
elseif ([long]$EventId -gt 65535 -or [long]$EventId -lt 0) {
Write-Host "[Error] Event ID '$EventId' is not a valid event id. Event ID's must be less than or equal to 65535 and greater than or equal to 0. Removing it from the search."
$ExitCode = 1
}
else {
$EventIdsToSearch.Add($EventId)
}
}
# Prepare a list to hold event IDs that should be excluded from the search
$EventsToExclude = New-Object System.Collections.Generic.List[int]
# Similar process for excluded event IDs as regular event IDs
if ($ExcludeEventIDs -and $ExcludeEventIDs -match ",") {
$ExcludeEventIDs -split "," | ForEach-Object {
$ExcludeEventId = $_.Trim()
if ($ExcludeEventId -match '[a-zA-Z]|\W') {
Write-Host "[Error] Event ID '$ExcludeEventId' is not a valid event id. Removing it from the exclusions."
$ExitCode = 1
return
}
if ([long]$ExcludeEventId -gt 65535 -or [long]$ExcludeEventId -lt 0) {
Write-Host "[Error] Event ID '$ExcludeEventId' is not a valid event id. Event ID's must be less than or equal to 65535 and greater than or equal to 0. Removing it from the exclusions."
$ExitCode = 1
return
}
$EventsToExclude.Add($ExcludeEventId)
}
}
elseif ($ExcludeEventIDs) {
$ExcludeEventId = $ExcludeEventIDs.Trim()
if ($ExcludeEventId -match '[a-zA-Z]|\W') {
Write-Host "[Error] Event ID '$ExcludeEventId' is not a valid event id. Removing it from the exclusions."
$ExitCode = 1
}
elseif ([long]$ExcludeEventId -gt 65535 -or [long]$ExcludeEventId -lt 0) {
Write-Host "[Error] Event ID '$ExcludeEventId' is not a valid event id. Event ID's must be less than or equal to 65535 and greater than or equal to 0. Removing it from the exclusions."
$ExitCode = 1
}
else {
$EventsToExclude.Add($ExcludeEventId)
}
}
# Check if there are any event IDs to exclude and if the list of event IDs to search for is not empty.
if ($EventsToExclude.Count -gt 0 -and $EventIdsToSearch.Count -gt 0) {
$EventsToExclude | ForEach-Object {
# Check if the current event ID from the exclusion list is also in the list of event IDs to search for.
if ($EventIdsToSearch -contains $_) {
Write-Warning "Event ID $_ has been specified for both inclusion and exclusion. It will be excluded."
}
}
}
# Check if there's no valid event ID, log name, or log source provided and exit if true
if ($EventIdsToSearch.Count -eq 0 -and !$EventLogName -and !$EventLogSource) {
Write-Host "[Error] No valid Event ID given and no Event Log Name or Event Log Source given."
exit 1
}
# Handy function to set a custom field.
function Set-NinjaProperty {
[CmdletBinding()]
Param(
[Parameter(Mandatory = $True)]
[String]$Name,
[Parameter()]
[String]$Type,
[Parameter(Mandatory = $True, ValueFromPipeline = $True)]
$Value,
[Parameter()]
[String]$DocumentName
)
$Characters = $Value | Out-String | Measure-Object -Character | Select-Object -ExpandProperty Characters
if ($Characters -ge 200000) {
throw [System.ArgumentOutOfRangeException]::New("Character limit exceeded, value with $Characters characters is greater than or equal to 200,000 characters.")
}
# If we're requested to set the field value for a Ninja document we'll specify it here.
$DocumentationParams = @{}
if ($DocumentName) { $DocumentationParams["DocumentName"] = $DocumentName }
# This is a list of valid fields that can be set. If no type is given, it will be assumed that the input doesn't need to be changed.
$ValidFields = "Attachment", "Checkbox", "Date", "Date or Date Time", "Decimal", "Dropdown", "Email", "Integer", "IP Address", "MultiLine", "MultiSelect", "Phone", "Secure", "Text", "Time", "URL", "WYSIWYG"
if ($Type -and $ValidFields -notcontains $Type) { Write-Warning "$Type is an invalid type! Please check here for valid types. https://ninjarmm.zendesk.com/hc/en-us/articles/16973443979789-Command-Line-Interface-CLI-Supported-Fields-and-Functionality" }
# The field below requires additional information to be set
$NeedsOptions = "Dropdown"
if ($DocumentName) {
if ($NeedsOptions -contains $Type) {
# We'll redirect the error output to the success stream to make it easier to error out if nothing was found or something else went wrong.
$NinjaPropertyOptions = Ninja-Property-Docs-Options -AttributeName $Name @DocumentationParams 2>&1
}
}
else {
if ($NeedsOptions -contains $Type) {
$NinjaPropertyOptions = Ninja-Property-Options -Name $Name 2>&1
}
}
# If an error is received it will have an exception property, the function will exit with that error information.
if ($NinjaPropertyOptions.Exception) { throw $NinjaPropertyOptions }
# The below type's require values not typically given in order to be set. The below code will convert whatever we're given into a format ninjarmm-cli supports.
switch ($Type) {
"Checkbox" {
# While it's highly likely we were given a value like "True" or a boolean datatype it's better to be safe than sorry.
$NinjaValue = [System.Convert]::ToBoolean($Value)
}
"Date or Date Time" {
# Ninjarmm-cli expects the GUID of the option to be selected. Therefore, the given value will be matched with a GUID.
$Date = (Get-Date $Value).ToUniversalTime()
$TimeSpan = New-TimeSpan (Get-Date "1970-01-01 00:00:00") $Date
$NinjaValue = $TimeSpan.TotalSeconds
}
"Dropdown" {
# Ninjarmm-cli is expecting the guid of the option we're trying to select. So we'll match up the value we were given with a guid.
$Options = $NinjaPropertyOptions -replace '=', ',' | ConvertFrom-Csv -Header "GUID", "Name"
$Selection = $Options | Where-Object { $_.Name -eq $Value } | Select-Object -ExpandProperty GUID
if (-not $Selection) {
throw [System.ArgumentOutOfRangeException]::New("Value is not present in dropdown")
}
$NinjaValue = $Selection
}
default {
# All the other types shouldn't require additional work on the input.
$NinjaValue = $Value
}
}
# We'll need to set the field differently depending on if its a field in a Ninja Document or not.
if ($DocumentName) {
$CustomField = Ninja-Property-Docs-Set -AttributeName $Name -AttributeValue $NinjaValue @DocumentationParams 2>&1
}
else {
$CustomField = $NinjaValue | Ninja-Property-Set-Piped -Name $Name 2>&1
}
if ($CustomField.Exception) {
throw $CustomField
}
}
function Test-IsElevated {
$id = [System.Security.Principal.WindowsIdentity]::GetCurrent()
$p = New-Object System.Security.Principal.WindowsPrincipal($id)
$p.IsInRole([System.Security.Principal.WindowsBuiltInRole]::Administrator)
}
if (!$ExitCode) {
$ExitCode = 0
}
}
process {
# Check if the script is running with elevated (Administrator) privileges
if (!(Test-IsElevated)) {
# If not, display an error message and exit with status code 1
Write-Host -Object "[Error] Access Denied. Please run with Administrator privileges."
exit 1
}
# Prepare a list to hold event log names to search for
$EventLogNamesToSearch = New-Object System.Collections.Generic.List[string]
# If no event log name was required we'll search all the event
if (!$EventLogName) {
$EventLogNamesOnSystem | Where-Object { $_.RecordCount -gt 0 } | Select-Object -ExpandProperty LogName | ForEach-Object {
$EventLogNamesToSearch.Add($_)
}
}
else {
$EventLogNamesToSearch.Add($EventLogName)
}
# Create XML object.
[xml]$XML = New-Object System.Xml.XmlDocument
# Add QueryList element to xml.
$QueryList = $XML.CreateElement("QueryList")
$QueryList = $XML.AppendChild($QueryList)
# Create query element and nest it under QueryList.
$Query = $XML.CreateElement("Query")
$Query.SetAttribute("Id", "0")
$Query = $QueryList.AppendChild($Query)
# Foreach event log to search we're going to create a select element.
$EventLogNamesToSearch | ForEach-Object {
# We'll start each loop by selecting the query element to add to.
$Query = $XML.SelectSingleNode("//Query")
# The select element starts off with the event log to search.
$Select = $XML.CreateElement("Select")
$Select.SetAttribute("Path", "$_")
# Reset the inner text between runnings
$XMLInnerText = $Null
# The inner text of each element (<Element1>InnerText</Element1>) will need to be built differently depending on the parameters.
if ($EventLogSource) {
$XMLInnerText = "*[System[Provider[@Name='$EventLogSource']]]"
}
# If we're given a select number of event id's to search we'll filter them here.
if ($EventIdsToSearch.Count -gt 0) {
$EventIDSearchText = $Null
$EventIdsToSearch | ForEach-Object {
# We may have been given one event id or more than one.
if ($EventIDSearchText) {
$EventIDSearchText = "$EventIDSearchText or EventID=$_"
}
else {
$EventIDSearchText = "EventID=$_"
}
}
# We'll replace the two ending brackets with our given search text
if ($XMLInnerText) {
$XMLInnerText = $XMLInnerText -replace ']]$', " and ($EventIDSearchText)]]"
}
else {
$XMLInnerText = "*[System[($EventIDSearchText)]]"
}
}
# If we're also asked to filter based on the date the event was created we'll create the filter text here.
if ($StartDate -or $EndDate) {
$DateFilter = $Null
if ($StartDate) {
$XMLstartDate = Get-Date $StartDate -Format "yyyy-MM-ddTHH:mm:ss"
# PowerShell will convert the < or > symbol for us when we go to save to the xml.
$DateFilter = "@SystemTime>='$XMLstartDate'"
}
# We may or may not have been given a start date.
if ($EndDate -and $DateFilter) {
$XMLendDate = Get-Date $EndDate -Format "yyyy-MM-ddTHH:mm:ss"
$DateFilter = "$DateFilter and @SystemTime<='$XMLendDate'"
}
elseif ($EndDate) {
$XMLendDate = Get-Date $EndDate -Format "yyyy-MM-ddTHH:mm:ss"
$DateFilter = "@SystemTime<='$XMLendDate'"
}
# Replace the last two closing brackets and add our filter text.
if($XMLInnerText){
$XMLInnerText = $XMLInnerText -replace ']]$', " and TimeCreated[$DateFilter]]]"
}else{
$XMLInnerText = "*[System[TimeCreated[$DateFilter]]]"
}
}
# If no filters were given (other than the event log name) we'll need to select everything in that log
if(!$XMLInnerText){
$XMLInnerText = "*"
}
# Save our filter text to the select statement
$Select.InnerText = $XMLInnerText
# Append our select statement to our xml file
$Query.AppendChild($Select) | Out-Null
}
# Search for matching events using the XML filter
$MatchingEvents = Get-WinEvent -FilterXml $XML -ErrorAction SilentlyContinue
# Exclude events based on the excluded event IDs if any are specified
if ($EventsToExclude.Count -gt 0) {
$MatchingEvents = $MatchingEvents | Where-Object { $EventsToExclude -notcontains $_.ID }
}
# Exclude events that do not match the keywords you specified.
if ($EventLogMessage) {
$MatchingEvents = $MatchingEvents | Where-Object { $_.Message -like "*$EventLogMessage*" }
}
# If the event log message is larger than 100 characters trim it and add ...
if ($MatchingEvents) {
$MatchingEvents = $MatchingEvents | Select-Object LevelDisplayName, LogName, ProviderName, Id, TimeCreated, @{
Name = 'Message'
Expression = {
$Characters = $_.Message | Measure-Object -Character | Select-Object -ExpandProperty Characters
if ($Characters -gt 100) {
"$(($_.Message).SubString(0,100))(...)"
}
else {
$_.Message
}
}
}
# Sort the object by newest event to oldest
$MatchingEvents = $MatchingEvents | Sort-Object TimeCreated -Descending
}
# Set a Wysiwyg custom field if any matching events are found and it was requested.
if ($WysiwygCustomField -and $MatchingEvents) {
try {
Write-Host "Attempting to set Custom Field '$WysiwygCustomField'."
# Prepare the custom field output.
$CustomFieldValue = New-Object System.Collections.Generic.List[string]
# Convert the matching events into an html report.
$htmlTable = $MatchingEvents | Select-Object -Property LevelDisplayName, LogName, ProviderName, Id, TimeCreated, Message | ConvertTo-Html -Fragment
# Set color coding
$htmlTable = $htmlTable -replace "<tr><td>Verbose</td>", "<tr class=`"other`"><td>Verbose</td>"
$htmlTable = $htmlTable -replace "<tr><td>Warning</td>", "<tr class=`"warning`"><td>Warning</td>"
$htmlTable = $htmlTable -replace "<tr><td>Error</td>", "<tr class=`"danger`"><td>Error</td>"
$htmlTable = $htmlTable -replace "<tr><td>Critical Error</td>", "<tr class=`"danger`"><td>Critical Error</td>"
# Remove Level Display Name
$LevelDisplayNames = $MatchingEvents | Select-Object -Property LevelDisplayName -Unique
$LevelDisplayNames | ForEach-Object {
$htmlTable = $htmlTable -replace "<td>$([Regex]::Escape($_.LevelDisplayName))</td>"
}
$htmlTable = $htmlTable -replace "<th>LevelDisplayName</th>"
# Add the newly created html into the custom field output.
$CustomFieldValue.Add($htmlTable)
# Check that the output complies with the hard character limits.
$Characters = $CustomFieldValue | Out-String | Measure-Object -Character | Select-Object -ExpandProperty Characters
if ($Characters -ge 199500) {
Write-Warning "200,000 Character Limit has been reached! Trimming output until the character limit is satisified..."
# If it doesn't comply with the limits we'll need to recreate it with some adjustments.
$i = 0
do {
# Recreate the custom field output starting with a warning that we truncated the output.
$CustomFieldValue = New-Object System.Collections.Generic.List[string]
$CustomFieldValue.Add("<h1>This info has been truncated to accommodate the 200,000 character limit.</h1>")
# The custom field information is sorted from newest to oldest. We'll remove the oldest first by flipping the array upside down.
[array]::Reverse($htmlTable)
# If the next entry is a row we'll delete it.
if ($htmlTable[$i] -match '<tr><td>' -or $htmlTable[$i] -match '<tr class=') {
$htmlTable[$i] = $null
}
$i++
# We'll flip the array back to right side up.
[array]::Reverse($htmlTable)
# Add it back to the output.
$CustomFieldValue.Add($htmlTable)
# Check that we now comply with the character limit. If not restart the do loop.
$Characters = $CustomFieldValue | Out-String | Measure-Object -Character | Select-Object -ExpandProperty Characters
}while ($Characters -ge 199500)
}
# Set the custom field.
Set-NinjaProperty -Name $WysiwygCustomField -Value $CustomFieldValue
Write-Host "Successfully set Custom Field '$WysiwygCustomField'!"
}
catch {
Write-Host "[Error] $($_.Exception.Message)"
$ExitCode = 1
}
}
# Set a multiline custom field if any matching events are found and it was requested.
if ($MultilineCustomField -and $MatchingEvents) {
try {
Write-Host "Attempting to set Custom Field '$MultilineCustomField'."
$CustomFieldValue = New-Object System.Collections.Generic.List[string]
# We don't want to edit the matching Events array if we have to truncate later so we'll create a duplicate here.
$CustomFieldList = $MatchingEvents | Select-Object -Property LogName, ProviderName, Id, TimeCreated, Message
# Format the matching items into a nice list with the relevant properties.
$CustomFieldValue.Add(($CustomFieldList | Format-List -Property LogName, ProviderName, Id, TimeCreated, Message | Out-String))
# Check that the output complies with the hard character limits.
$Characters = $CustomFieldValue | Out-String | Measure-Object -Character | Select-Object -ExpandProperty Characters
if ($Characters -ge 9500) {
Write-Warning "10,000 Character Limit has been reached! Trimming output until the character limit is satisified..."
# If it doesn't comply with the limits we'll need to recreate it with some adjustments.
$i = 0
do {
# Recreate the custom field output starting with a warning that we truncated the output.
$CustomFieldValue = New-Object System.Collections.Generic.List[string]
$CustomFieldValue.Add("This info has been truncated to accommodate the 10,000 character limit.")
# The custom field information is sorted from newest to oldest. We'll remove the oldest events first by flipping the array upside down.
[array]::Reverse($CustomFieldList)
# Remove the next item which in this case will be the oldest item.
$CustomFieldList[$i] = $null
$i++
# We'll flip the array back to right side up.
[array]::Reverse($CustomFieldList)
# Add it back to the output.
$CustomFieldValue.Add(($CustomFieldList | Format-List -Property LogName, ProviderName, Id, TimeCreated, Message | Out-String))
# Check that we now comply with the character limit. If not restart the do loop.
$Characters = $CustomFieldValue | Out-String | Measure-Object -Character | Select-Object -ExpandProperty Characters
}while ($Characters -ge 9500)
}
Set-NinjaProperty -Name $MultilineCustomField -Value $CustomFieldValue
Write-Host "Successfully set Custom Field '$MultilineCustomField'!"
}
catch {
Write-Host "[Error] $($_.Exception.Message)"
$ExitCode = 1
}
}
# If any matching events were found output them into the activity log.
if ($MatchingEvents) {
Write-Host "Matching Events Found!"
$MatchingEvents | Format-List LogName, ProviderName, Id, TimeCreated, Message | Out-String | Write-Host
}
else {
Write-Host "No matching events found!"
}
exit $ExitCode
}
end {
}
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Understanding the PowerShell Script
This PowerShell script is a versatile tool that allows users to search for specific events in the Event Viewer based on various criteria. The script can filter events by log name, source, event ID, message content, and date range. Additionally, it provides options to exclude certain event IDs from the search and to store the results in custom fields.
Here’s a detailed breakdown of how the script functions:
1. Parameters and Environment Variables:
- The script begins by setting parameters that allow users to define their search criteria, such as EventLogName, EventLogSource, EventIDs, StartDate, and EndDate. It also supports environment variables for these parameters, enabling integration with other automation workflows.
2. Validation and Error Handling:
- The script includes multiple layers of validation to ensure that the input parameters are correct. For example, it checks whether the provided start date is earlier than the end date and validates that event IDs are numeric and within the acceptable range.
- If the WysiwygCustomField and MultilineCustomField parameters are set to the same value, the script throws an error, preventing conflicting configurations.
3. Event Log Search Logic:
- The script constructs an XML query to filter events based on the provided criteria. This query is then used with the Get-WinEvent cmdlet to retrieve matching events from the specified logs.
- The script allows for the exclusion of certain event IDs and can filter events by message content, making it highly customizable.
4. Custom Field Setting:
- If matching events are found, the script can store the results in custom fields, either as a multiline text field or as an HTML-formatted report. This feature is particularly useful for MSPs who need to document findings or automate reporting.
5. Output and Sorting:
- The script outputs the results in a readable format, sorted by the time the events were created, from newest to oldest. It also trims long messages to avoid overwhelming the output.
Practical Applications of the Script
Consider a scenario where an IT professional is tasked with identifying recurring errors across multiple servers in a corporate environment. Manually sifting through event logs on each server would be time-consuming and error-prone.
By leveraging this PowerShell script, the professional can automate the search process, filtering logs based on specific error event IDs and narrowing the results to a particular time frame. This approach not only saves time but also improves accuracy, allowing the IT team to quickly diagnose and resolve issues.
Another use case could involve compliance auditing. An MSP might need to verify that certain security events, such as successful or failed login attempts, are occurring as expected across their managed systems. This script can be used to extract these events and generate reports that demonstrate compliance with security policies.
Comparing Approaches to Event Log Searches
While there are several methods to search event logs, including using the built-in Event Viewer GUI or other third-party tools, this PowerShell script offers distinct advantages. Unlike manual searches through the GUI, this script can be automated and integrated into larger workflows. Additionally, compared to other tools, PowerShell provides a high degree of customization, allowing IT professionals to tailor the search criteria to their specific needs.
Frequently Asked Questions
Q: Can this script be used on systems running older versions of Windows?
A: The script requires Windows PowerShell 5.1 and is supported on Windows 10 and Windows Server 2016 or later.
Q: What happens if the character limit is exceeded when setting a custom field?
A: The script includes logic to truncate the output to fit within the character limit, ensuring that the script does not fail due to overly large data sets.
Q: Is it possible to search all event logs on a system using this script?
A: Yes, if no specific event log name is provided, the script will search through all available event logs on the system.
Implications for IT Security
The ability to efficiently search event logs has significant implications for IT security. By quickly identifying suspicious or anomalous events, IT professionals can respond to potential security incidents more effectively. The automation provided by this script reduces the risk of human error and ensures that critical events are not overlooked.
Best Practices for Using the Script
- Always test the script in a controlled environment before deploying it in production.
- Use environment variables to integrate the script into larger automation workflows.
- Regularly update the script to incorporate new features or address potential security vulnerabilities.
Final Thoughts
Efficient event log management is essential for maintaining system health, ensuring security, and achieving compliance. This PowerShell script provides IT professionals with a powerful tool for searching and analyzing event logs, enabling them to perform their duties more effectively.
For MSPs and IT teams managing multiple systems, NinjaOne offers a comprehensive suite of tools that can further enhance your ability to monitor and manage your IT infrastructure. By integrating this script into your workflows, you can streamline your event log searches and improve your overall IT operations.
