Detect Remote Email Collection in Google Chronicle
Adversaries may target an Exchange server, Office 365, or Google Workspace to collect sensitive information. Adversaries may leverage a user's credentials and interact directly with the Exchange server to acquire information from within a network. Adversaries may also access externally facing Exchange services, Office 365, or Google Workspace to access email using credentials or access tokens. Tools such as MailSniper can be used to automate searches for specific keywords.
MITRE ATT&CK
- Tactic
- Collection
- Technique
- T1114 Email Collection
- Sub-technique
- T1114.002 Remote Email Collection
- Canonical reference
- https://attack.mitre.org/techniques/T1114/002/
YARA-L Detection Query
rule remote_email_collection_t1114_002 {
meta:
author = "Argus Detection Engineering"
description = "Detects remote email collection via Exchange collection cmdlets or suspicious EWS tooling (T1114.002)"
mitre_attack_technique = "T1114.002"
mitre_attack_tactic = "Collection"
severity = "HIGH"
priority = "HIGH"
reference = "https://attack.mitre.org/techniques/T1114/002/"
events:
(
(
$e.metadata.event_type = "PROCESS_LAUNCH" and
re.regex($e.target.process.file.full_path,
`(?i)(powershell\.exe|pwsh\.exe|exshell\.exe)`) and
re.regex($e.target.process.command_line,
`(?i)(New-MailboxExportRequest|Get-MailboxExportRequest|Search-Mailbox|New-ComplianceSearch|Start-ComplianceSearch|New-ComplianceSearchAction|Get-ComplianceSearchAction|Invoke-SelfSearch|Invoke-GlobalMailSearch|Get-GlobalAddressList|Invoke-MailboxSearch|New-MailboxSearch|MailSniper|Microsoft\.Exchange\.WebServices|EWSEditor|Invoke-PasswordSprayOWA)`)
) or
(
$e.metadata.event_type = "NETWORK_HTTP" and
re.regex($e.network.http.user_agent,
`(?i)(MailSniper|python-requests|python/[0-9]|Go-http-client|curl/[0-9]|wget/|Microsoft\.Exchange\.WebServices|EWSEditor)`)
) or
(
$e.metadata.product_name = "Office 365" and
$e.metadata.event_type = "USER_RESOURCE_ACCESS" and
re.regex($e.metadata.description,
`(?i)(New-MailboxExportRequest|Search-Mailbox|New-ComplianceSearch|Invoke-MailboxSearch|Get-GlobalAddressList|MailSniper|Invoke-SelfSearch|Invoke-GlobalMailSearch)`)
)
)
condition:
$e
}Detects remote email collection (T1114.002) across three telemetry branches in Chronicle UDM: PowerShell execution of Exchange collection cmdlets on endpoints, suspicious EWS HTTP client user agents at the network layer, and Office 365 audit events capturing known collection operations. Uses re.regex for flexible pattern matching across all branches.
Data Sources
Required Tables
False Positives & Tuning
- Authorized eDiscovery workflows using compliance search cmdlets initiated by legal or compliance teams
- Exchange Online migration tooling using EWS SDK with scripted HTTP clients during mail migration projects
- Security monitoring tools that use Exchange Web Services to inspect email metadata for DLP or archiving purposes
Other platforms for T1114.002
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1MailSniper — Invoke-SelfSearch for Credential Keywords
Expected signal: Sysmon Event ID 1: Process Create for powershell.exe with CommandLine containing 'MailSniper', 'Invoke-SelfSearch', and keyword terms. Sysmon Event ID 3: Network connection from powershell.exe to the Exchange server on port 443 (HTTPS/EWS). PowerShell ScriptBlock Log Event ID 4104 with full MailSniper invocation. On the Exchange side: IIS access logs will show EWS hits from the test workstation with a non-Outlook user agent.
- Test 2New-MailboxExportRequest — Export Mailbox to PST
Expected signal: Exchange Admin Audit Log: New-MailboxExportRequest entry with Mailbox, FilePath, and requester identity. Office 365 OfficeActivity RecordType=ExchangeAdmin, Operation=New-MailboxExportRequest. File creation on the target UNC path (Sysmon Event ID 11 on the destination host). PowerShell Event ID 4104 with full cmdlet invocation.
- Test 3EWS Direct Access via PowerShell (Microsoft.Exchange.WebServices)
Expected signal: Sysmon Event ID 7: Image Load for Microsoft.Exchange.WebServices.dll loaded by powershell.exe. Sysmon Event ID 3: Network connection from powershell.exe to Exchange server port 443. IIS logs on Exchange CAS showing EWS request from workstation with user agent 'ExchangeServicesClient/15.00.0000.000' or similar non-Outlook agent. PowerShell ScriptBlock Log Event ID 4104 with EWS API invocation.
- Test 4Remote OST File Access via UNC Path (Chimera Technique)
Expected signal: Sysmon Event ID 11: File Create at %TEMP%\stolen_email.ost. Sysmon Event ID 10 or Windows Security Event ID 4663 (if Object Access auditing is enabled): access to the .ost file in %LOCALAPPDATA%\Microsoft\Outlook. If performed remotely, SMB access events (Event ID 5140 — A network share object was accessed) for the C$ administrative share on the source host. PowerShell Event ID 4104 with file copy invocation.
References (12)
- https://attack.mitre.org/techniques/T1114/002/
- https://github.com/dafthack/MailSniper
- https://learn.microsoft.com/en-us/exchange/policy-and-compliance/mailbox-audit-logging/mailbox-audit-logging
- https://learn.microsoft.com/en-us/microsoft-365/compliance/search-for-and-delete-messages-in-your-organization
- https://learn.microsoft.com/en-us/exchange/recipients/mailbox-import-and-export/export-procedures
- https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
- https://www.mandiant.com/resources/blog/apt29-microsoft-365-email-collection
- https://research.nccgroup.com/2021/01/12/abusing-exchange-one-api-call-away-from-domain-admin/
- https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/
- https://www.microsoft.com/security/blog/2021/12/06/nickel-targeting-government-organizations-across-latin-america-and-europe/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1114.002/T1114.002.md
- https://www.cisa.gov/sites/default/files/2023-12/aa23-347a_star-blizzard-advisory.pdf
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