LoFP LoFP / legitimate exchange system administration activity.

Techniques

Sample rules

New ActiveSyncAllowedDeviceID Added via PowerShell

Description

Identifies the use of the Exchange PowerShell cmdlet, Set-CASMailbox, to add a new ActiveSync allowed device. Adversaries may target user email to collect sensitive information.

Detection logic

process where host.os.type == "windows" and event.type == "start" and
  process.name: ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and process.args : "Set-CASMailbox*ActiveSyncAllowedDeviceIDs*"

Exchange Mailbox Export via PowerShell

Description

Detects PowerShell script block content that creates Exchange mailbox export requests via New-MailboxExportRequest, commonly writing PST files. Adversaries can abuse export requests to collect and stage email content for exfiltration.

Detection logic

event.category:process and host.os.type:windows and
powershell.file.script_block_text : "New-MailboxExportRequest" and
(
  powershell.file.script_block_text : ("-FilePath" or ".pst") and
  powershell.file.script_block_text : ("-Mailbox" or "Get-Mailbox" or "ExportToPSTFile" or "-Identity")
)

Exporting Exchange Mailbox via PowerShell

Description

Identifies the use of the Exchange PowerShell cmdlet, New-MailBoxExportRequest, to export the contents of a primary mailbox or archive to a .pst file. Adversaries may target user email to collect sensitive information.

Detection logic

process where host.os.type == "windows" and event.type == "start" and
  process.name: ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and
  process.command_line : ("*MailboxExportRequest*", "*-Mailbox*-ContentFilter*")