T1087.003

Email Account

Adversaries may attempt to get a listing of email addresses and accounts. Adversaries may try to dump Exchange address lists such as global address lists (GALs). In on-premises Exchange and Exchange Online, the Get-GlobalAddressList PowerShell cmdlet can be used to obtain email addresses and accounts from a domain using an authenticated session. Threat actors including Magic Hound, TA505, RedCurl, and Sandworm Team have leveraged this technique using tools like MailSniper, Ruler, and custom malware to harvest email account information for reconnaissance, phishing, and lateral movement.

Microsoft Sentinel / Defender
kusto
let GALCmdlets = dynamic([
  "Get-GlobalAddressList", "Get-AddressList", "Get-OfflineAddressBook",
  "Get-Recipient", "Get-MailUser", "Get-Mailbox", "Get-GAL"
]);
let MailSniperPatterns = dynamic([
  "MailSniper", "Invoke-GlobalO365PasswordSpray", "Get-GlobalAddressList",
  "Invoke-SelfSearch", "Invoke-PasswordSprayOWA", "Invoke-PasswordSprayEWS"
]);
let OutlookPSTPatterns = dynamic([
  ".pst", ".ost", "OUTLOOK.EXE", "outlook.exe"
]);
// Detection 1: PowerShell GAL enumeration
let PSGALEnum = DeviceProcessEvents
| where Timestamp > ago(24h)
| where FileName in~ ("powershell.exe", "pwsh.exe")
| where ProcessCommandLine has_any (GALCmdlets) or ProcessCommandLine has_any (MailSniperPatterns)
| extend DetectionType = "PowerShell_GAL_Enumeration"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
         InitiatingProcessFileName, InitiatingProcessCommandLine, DetectionType;
// Detection 2: Exchange PowerShell remote session for address enumeration
let ExchangePSEnum = DeviceProcessEvents
| where Timestamp > ago(24h)
| where FileName in~ ("powershell.exe", "pwsh.exe")
| where ProcessCommandLine has "ExchangeManagementShell" or
        (ProcessCommandLine has "New-PSSession" and ProcessCommandLine has_any ("outlook", "exchange", "office365", "outlook.office365.com")) or
        (ProcessCommandLine has "Connect-ExchangeOnline" and ProcessCommandLine has_any (GALCmdlets))
| extend DetectionType = "Exchange_Remote_Session_Enum"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
         InitiatingProcessFileName, InitiatingProcessCommandLine, DetectionType;
// Detection 3: LDAP queries targeting email attributes
let LDAPEmailEnum = DeviceProcessEvents
| where Timestamp > ago(24h)
| where ProcessCommandLine has "LDAP" and
        (ProcessCommandLine has "mail" or ProcessCommandLine has "proxyAddresses" or
         ProcessCommandLine has "targetAddress" or ProcessCommandLine has "msExch")
| extend DetectionType = "LDAP_Email_Attribute_Query"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
         InitiatingProcessFileName, InitiatingProcessCommandLine, DetectionType;
// Detection 4: Outlook PST/OST file access by non-Outlook processes
let OutlookFileEnum = DeviceFileEvents
| where Timestamp > ago(24h)
| where FolderPath has_any (".pst", ".ost")
| where not(InitiatingProcessFileName =~ "outlook.exe")
| where not(InitiatingProcessFileName in~ ("svchost.exe", "services.exe", "MicrosoftEdge.exe"))
| extend DetectionType = "Non_Outlook_PST_OST_Access"
| project Timestamp, DeviceName, AccountName = InitiatingProcessAccountName,
         FileName = InitiatingProcessFileName,
         ProcessCommandLine = InitiatingProcessCommandLine,
         InitiatingProcessFileName, InitiatingProcessCommandLine, DetectionType;
union PSGALEnum, ExchangePSEnum, LDAPEmailEnum, OutlookFileEnum
| sort by Timestamp desc
medium severity high confidence

Data Sources

Process: Process Creation Command: Command Execution File: File Access Microsoft Defender for Endpoint

Required Tables

DeviceProcessEvents DeviceFileEvents

False Positives

  • Exchange administrators legitimately running Get-GlobalAddressList or Get-Recipient cmdlets for address book management or auditing
  • Email migration tools (MigrationWiz, Bit Titan, IMAPMIG) accessing PST/OST files or querying address lists during migration projects
  • Backup software (Veeam Backup for Microsoft 365, Barracuda) accessing Outlook data files as part of scheduled backup jobs
  • IT helpdesk automation scripts using Exchange PowerShell to look up user mailbox information for troubleshooting
  • Third-party GAL synchronization tools used in hybrid Exchange environments accessing address list data

Unlock Pro Content

Get the full detection package for T1087.003 including response playbook, investigation guide, and atomic red team tests.

Response PlaybookInvestigation GuideHunting QueriesAtomic Red Team TestsTuning Guidance

Related Detections