Detect Email Collection in Splunk
Adversaries may target user email to collect sensitive information. Emails may contain sensitive data, including trade secrets or personal information, that can prove valuable to adversaries. Emails may also contain details of ongoing incident response operations, which may allow adversaries to adjust their techniques to maintain persistence or evade defenses. Adversaries can collect or forward email from mail servers or clients. Sub-techniques cover local email file access (T1114.001), remote server collection via EWS/IMAP (T1114.002), and persistent inbox forwarding rules (T1114.003). Threat actors including Ember Bear, Silent Librarian, Magic Hound, Scattered Spider, and Emotet have all leveraged email collection as a high-value intelligence gathering technique.
MITRE ATT&CK
- Tactic
- Collection
- Technique
- T1114 Email Collection
- Canonical reference
- https://attack.mitre.org/techniques/T1114/
SPL Detection Query
// T1114 Email Collection — Sysmon file access to local email data stores
// Detects non-email-client processes accessing PST/OST/MBOX/MSG email files
(index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=11
(TargetFilename="*.pst" OR TargetFilename="*.ost" OR TargetFilename="*.mbox"
OR TargetFilename="*.eml" OR TargetFilename="*.msg" OR TargetFilename="*.dbx" OR TargetFilename="*.nsf")
NOT (
Image="*\\outlook.exe" OR Image="*\\OUTLOOK.EXE"
OR Image="*\\thunderbird.exe"
OR Image="*\\SearchIndexer.exe"
OR Image="*\\SearchProtocolHost.exe"
OR Image="*\\MsMpEng.exe"
OR Image="*\\MsSense.exe"
)
)
| eval SuspicionScore=0
| eval SuspicionScore=if(match(Image, "(?i)(powershell\.exe|pwsh\.exe|cmd\.exe|python[23]?\.exe|wscript\.exe|cscript\.exe|mshta\.exe)"), SuspicionScore+3, SuspicionScore)
| eval SuspicionScore=if(match(Image, "(?i)(robocopy\.exe|xcopy\.exe|7z\.exe|winrar\.exe|rar\.exe|curl\.exe|wget\.exe)"), SuspicionScore+3, SuspicionScore)
| eval SuspicionScore=if(match(lower(TargetFilename), "(appdata.*outlook|appdata.*thunderbird|appdata.*windows mail)"), SuspicionScore+2, SuspicionScore)
| eval SuspicionScore=if(match(TargetFilename, "(?i)(\.pst$|\.ost$)"), SuspicionScore+1, SuspicionScore)
| eval EmailFileType=case(
match(TargetFilename, "(?i)\.pst$"), "OutlookPST",
match(TargetFilename, "(?i)\.ost$"), "OutlookOST",
match(TargetFilename, "(?i)\.mbox$"), "MboxArchive",
match(TargetFilename, "(?i)\.msg$"), "OutlookMessage",
match(TargetFilename, "(?i)\.eml$"), "EmailFile",
1==1, "OtherEmailFile")
| where SuspicionScore > 0
| eval AccountName=if(isnull(User), "Unknown", User)
| table _time, host, AccountName, Image, CommandLine, TargetFilename, EmailFileType, SuspicionScore
| sort - SuspicionScore, - _timeDetects email collection activity using Sysmon Event ID 11 (FileCreate) to identify non-email-client processes interacting with local email data stores. Assigns a cumulative suspicion score based on initiating process type (scripting engines and archive tools score highest at +3) and target file path (AppData Outlook/Thunderbird paths score +2). PST/OST files score an additional +1 as the highest-value collection targets. Filters out known legitimate email clients, search indexers, and AV engines to reduce noise.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Enterprise backup agents accessing PST/OST files during scheduled backup windows — add backup agent process paths to the NOT exclusion list
- Email migration tools (PST import utilities, MigrationWiz agent) performing authorized mailbox data operations during announced migration projects
- Anti-virus or EDR agents with non-standard process names that perform file scanning — extend the exclusion list with verified scanner paths
- IT automation scripts (SCCM baseline scripts, auditing tools) inventorying email archive files — coordinate expected script hashes with change management
- User-initiated archive operations using 7-Zip or WinRAR to compress old PST files for storage — may be legitimate but warrants confirmation with the user
Other platforms for T1114
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 1Copy Outlook PST/OST Files via PowerShell to Staging Directory
Expected signal: Sysmon Event ID 1: Process Create with Image=powershell.exe, CommandLine containing 'Get-ChildItem', 'Outlook', 'Copy-Item'. Sysmon Event ID 11: File creation events in %TEMP%\email_staging for each OST/PST copied. DeviceFileEvents (MDE): FileCopied action for .ost/.pst files with InitiatingProcessFileName=powershell.exe. DeviceProcessEvents: PowerShell process with command line referencing Outlook and Copy-Item.
- Test 2Enumerate Outlook Inbox via COM Object (MAPI)
Expected signal: Sysmon Event ID 1: PowerShell process with CommandLine containing 'Outlook.Application', 'MAPI', 'GetDefaultFolder'. Sysmon Event ID 7 (ImageLoad): Outlook interop DLLs (olmapi32.dll, MSPST32.dll) loaded into powershell.exe process. Sysmon Event ID 11: CSV file created at %TEMP%\email_harvest.csv. DeviceImageLoadEvents (MDE): non-Outlook process loading Outlook MAPI libraries.
- Test 3Remote Exchange Mailbox Enumeration via EWS SOAP Request
Expected signal: Sysmon Event ID 3: Network connection from powershell.exe to outlook.office365.com (40.99.x.x range) on destination port 443. DeviceNetworkEvents (MDE): OutboundConnectionAttempt or ConnectionSuccess from powershell.exe to Microsoft O365 EWS IP. PowerShell ScriptBlock Log (Event ID 4104): full SOAP request body including 'FindItem', 'inbox', 'EWS' strings. O365 Unified Audit Log: failed or successful MailItemsAccessed operation depending on authentication outcome.
- Test 4Create Malicious Inbox Forwarding Rule via Exchange Online PowerShell
Expected signal: Sysmon Event ID 1: PowerShell process with CommandLine containing 'New-InboxRule', 'ForwardTo', and target email address. PowerShell ScriptBlock Log (Event ID 4104): full script with New-InboxRule command and ForwardTo parameter value. O365 Unified Audit Log (if connection succeeds): New-InboxRule operation with Parameters showing [email protected]. Sysmon Event ID 3: PowerShell connecting to O365 PowerShell endpoint (*.outlook.com port 443).
References (9)
- https://attack.mitre.org/techniques/T1114/
- https://www.cisa.gov/news-events/cybersecurity-advisories/aa20-352a
- https://blogs.technet.microsoft.com/timmcmic/2015/06/08/exchange-and-office-365-mail-forwarding-2/
- https://trustedsec.com/blog/to-oob-or-not-to-oob-why-out-of-band-communications-are-essential-for-incident-response
- https://learn.microsoft.com/en-us/microsoft-365/compliance/search-the-audit-log-in-security-and-compliance
- https://learn.microsoft.com/en-us/exchange/policy-and-compliance/mailbox-audit-logging/mailbox-audit-logging
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1114/T1114.md
- https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-320a
- https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/anti-phishing-policies-about
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