Identifying Macro-Related Mail Flow Rules in Exchange Online

In today’s email security landscape, macros embedded in documents are a common vector for malware attacks. Ensuring that your organization’s mail flow rules in Exchange Online are correctly configured to handle macro-related content is crucial for maintaining security.

This article provides a guide on using PowerShell to identify mail flow rules that address macro-related content. The script checks for conditions that reference file extensions commonly associated with macros and actions that block or manage such emails. This helps administrators ensure that their mail flow rules effectively mitigate the risk of macro-based threats.

Here is the script:

Connect to Exchange Online

Connect-ExchangeOnline

Get all mail flow rules

$rules = Get-TransportRule

Initialize an array to store results

$results = @()

Check each rule for macro-related content

foreach ($rule in $rules) { $ruleName = $rule.Name $actions = $rule.Actions $conditions = $rule.Conditions

Check if any condition references file extensions commonly associated with macros

$macroConditions = $conditions | Where-Object { $.AttachmentExtension -contains “xlsm” -or $.AttachmentExtension -contains “docm” -or $.AttachmentExtension -contains “pptm” -or $.SubjectContainsWords -contains “macro” }

Check if any action is related to blocking or rejecting messages

$blockActions = $actions | Where-Object { $.RejectMessageReasonText -like “macro” -or $.DeleteMessage -eq $true -or $_.RedirectMessageTo -ne $null }

if ($macroConditions -and $blockActions) { $results += [PSCustomObject]@{ RuleName = $ruleName Actions = $actions Conditions = $conditions } } }

Output results

if ($results.Count -gt 0) { $results | Format-Table -AutoSize } else { Write-Output “No mail flow rules found that block or handle macros.” }

Disconnect from Exchange Online

Disconnect-ExchangeOnline -Confirm:$false