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Suspicious MS Outlook Child Process

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Suspicious MS Outlook Child Process

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Identifies suspicious child processes of Microsoft Outlook. These child processes are often associated with spear phishing activity.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: low

Risk score: 21

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Initial Access
  • Investigation Guide

Version: 102 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guide

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## Triage and analysis

### Investigating Suspicious MS Outlook Child Process

Microsoft Outlook is an email client that provides contact, email calendar, and task management features. Outlook is
widely used, either standalone or as part of the Office suite.

This rule looks for suspicious processes spawned by MS Outlook, which can be the result of the execution of malicious
documents and/or exploitation for initial access.

#### Possible investigation steps

- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Retrieve recently opened files received via email and opened by the user that could cause this behavior. Common
locations include but are not limited to, the Downloads and Document folders and the folder configured at the email client.
- Determine if the collected files are malicious:
  - Use a private sandboxed malware analysis system to perform analysis.
    - Observe and collect information about the following activities:
      - Attempts to contact external domains and addresses.
      - File and registry access, modification, and creation activities.
      - Service creation and launch activities.
      - Scheduled task creation.
  - Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
    - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.

### False positive analysis

- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved host to prevent further post-compromise behavior.
- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
systems, and web services.
- If the triage identified malware, search the environment for additional compromised hosts.
  - Implement temporary network rules, procedures, and segmentation to contain the malware.
  - Stop suspicious processes.
  - Immediately block the identified indicators of compromise (IoCs).
  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
  attackers could use to reinfect the system.
- Remove and block malicious artifacts identified during triage.
- Run a full scan using the antimalware tool in place. This scan can reveal additional artifacts left in the system,
persistence mechanisms, and malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  - If the malicious file was delivered via phishing:
    - Block the email sender from sending future emails.
    - Block the malicious web pages.
    - Remove emails from the sender from mailboxes.
    - Consider improvements to the security awareness program.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).

Rule query

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process where event.type == "start" and process.parent.name :
"outlook.exe" and process.name : ("Microsoft.Workflow.Compiler.exe",
"arp.exe", "atbroker.exe", "bginfo.exe", "bitsadmin.exe",
"cdb.exe", "certutil.exe", "cmd.exe", "cmstp.exe", "cscript.exe",
"csi.exe", "dnx.exe", "dsget.exe", "dsquery.exe",
"forfiles.exe", "fsi.exe", "ftp.exe", "gpresult.exe", "hostname.exe",
"ieexec.exe", "iexpress.exe", "installutil.exe",
"ipconfig.exe", "mshta.exe", "msxsl.exe", "nbtstat.exe", "net.exe",
"net1.exe", "netsh.exe", "netstat.exe", "nltest.exe", "odbcconf.exe",
"ping.exe", "powershell.exe", "pwsh.exe",
"qprocess.exe", "quser.exe", "qwinsta.exe", "rcsi.exe", "reg.exe",
"regasm.exe", "regsvcs.exe", "regsvr32.exe",
"sc.exe", "schtasks.exe", "systeminfo.exe", "tasklist.exe",
"tracert.exe", "whoami.exe", "wmic.exe", "wscript.exe", "xwizard.exe")

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 102 (8.6.0 release)
  • Formatting only
Version 101 (8.5.0 release)

  • Updated query, changed from:

    process where event.type in ("start", "process_started") and
process.parent.name : "outlook.exe" and process.name :
("Microsoft.Workflow.Compiler.exe", "arp.exe", "atbroker.exe",
"bginfo.exe", "bitsadmin.exe", "cdb.exe",
"certutil.exe", "cmd.exe", "cmstp.exe", "cscript.exe", "csi.exe",
"dnx.exe", "dsget.exe", "dsquery.exe",
"forfiles.exe", "fsi.exe", "ftp.exe", "gpresult.exe", "hostname.exe",
"ieexec.exe", "iexpress.exe", "installutil.exe",
"ipconfig.exe", "mshta.exe", "msxsl.exe", "nbtstat.exe", "net.exe",
"net1.exe", "netsh.exe", "netstat.exe", "nltest.exe", "odbcconf.exe",
"ping.exe", "powershell.exe", "pwsh.exe",
"qprocess.exe", "quser.exe", "qwinsta.exe", "rcsi.exe", "reg.exe",
"regasm.exe", "regsvcs.exe", "regsvr32.exe",
"sc.exe", "schtasks.exe", "systeminfo.exe", "tasklist.exe",
"tracert.exe", "whoami.exe", "wmic.exe", "wscript.exe", "xwizard.exe")
Version 12 (8.4.0 release)
  • Formatting only
Version 10 (8.2.0 release)
  • Formatting only
Version 9 (7.13.0 release)

  • Updated query, changed from:

    event.category:process and event.type:(start or process_started) and
process.parent.name:outlook.exe and
process.name:(Microsoft.Workflow.Compiler.exe or arp.exe or
atbroker.exe or bginfo.exe or bitsadmin.exe or cdb.exe or
certutil.exe or cmd.exe or cmstp.exe or cscript.exe or csi.exe or
dnx.exe or dsget.exe or dsquery.exe or forfiles.exe or fsi.exe or
ftp.exe or gpresult.exe or hostname.exe or ieexec.exe or iexpress.exe
or installutil.exe or ipconfig.exe or mshta.exe or msxsl.exe or
nbtstat.exe or net.exe or net1.exe or netsh.exe or netstat.exe or
nltest.exe or odbcconf.exe or ping.exe or powershell.exe or pwsh.exe
or qprocess.exe or quser.exe or qwinsta.exe or rcsi.exe or reg.exe or
regasm.exe or regsvcs.exe or regsvr32.exe or sc.exe or schtasks.exe or
systeminfo.exe or tasklist.exe or tracert.exe or whoami.exe or
wmic.exe or wscript.exe or xwizard.exe)
Version 8 (7.12.0 release)
  • Formatting only
Version 7 (7.11.2 release)
  • Formatting only
Version 6 (7.11.0 release)
  • Formatting only
Version 5 (7.10.0 release)
  • Formatting only
Version 4 (7.9.1 release)
  • Formatting only
Version 3 (7.9.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.parent.name:outlook.exe and
process.name:(Microsoft.Workflow.Compiler.exe or arp.exe or
atbroker.exe or bginfo.exe or bitsadmin.exe or cdb.exe or certutil.exe
or cmd.exe or cmstp.exe or cscript.exe or csi.exe or dnx.exe or
dsget.exe or dsquery.exe or forfiles.exe or fsi.exe or ftp.exe or
gpresult.exe or hostname.exe or ieexec.exe or iexpress.exe or
installutil.exe or ipconfig.exe or mshta.exe or msxsl.exe or
nbtstat.exe or net.exe or net1.exe or netsh.exe or netstat.exe or
nltest.exe or odbcconf.exe or ping.exe or powershell.exe or pwsh.exe
or qprocess.exe or quser.exe or qwinsta.exe or rcsi.exe or reg.exe or
regasm.exe or regsvcs.exe or regsvr32.exe or sc.exe or schtasks.exe or
systeminfo.exe or tasklist.exe or tracert.exe or whoami.exe or
wmic.exe or wscript.exe or xwizard.exe)
Version 2 (7.7.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.parent.name:"outlook.exe" and process.name:("arp.exe" or
"dsquery.exe" or "dsget.exe" or "gpresult.exe" or "hostname.exe" or
"ipconfig.exe" or "nbtstat.exe" or "net.exe" or "net1.exe" or
"netsh.exe" or "netstat.exe" or "nltest.exe" or "ping.exe" or
"qprocess.exe" or "quser.exe" or "qwinsta.exe" or "reg.exe" or
"sc.exe" or "systeminfo.exe" or "tasklist.exe" or "tracert.exe" or
"whoami.exe" or "bginfo.exe" or "cdb.exe" or "cmstp.exe" or "csi.exe"
or "dnx.exe" or "fsi.exe" or "ieexec.exe" or "iexpress.exe" or
"installutil.exe" or "Microsoft.Workflow.Compiler.exe" or
"msbuild.exe" or "mshta.exe" or "msxsl.exe" or "odbcconf.exe" or
"rcsi.exe" or "regsvr32.exe" or "xwizard.exe" or "atbroker.exe" or
"forfiles.exe" or "schtasks.exe" or "regasm.exe" or "regsvcs.exe" or
"cmd.exe" or "cscript.exe" or "powershell.exe" or "pwsh.exe" or
"wmic.exe" or "wscript.exe" or "bitsadmin.exe" or "certutil.exe" or
"ftp.exe")
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