Suspicious Process Creation CallTraceedit

Identifies when a process is created and immediately accessed from an unknown memory code region and by the same parent process. This may indicate a code injection attempt.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-windows.*

Severity: medium

Risk score: 47

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
  • Defense Evasion
  • Investigation Guide
  • Sysmon Only

Version: 102 (version history)

Added (Elastic Stack release): 8.0.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guideedit

## Triage and analysis

### Investigating Suspicious Process Creation CallTrace

Attackers may inject code into child processes' memory to hide their actual activity, evade detection mechanisms, and
decrease discoverability during forensics. This rule looks for a spawned process by Microsoft Office, scripting, and
command line applications, followed by a process access event for an unknown memory region by the parent process, which
can indicate a code injection attempt.

#### 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 abnormal behavior observed by the subject process such as network connections, registry or file
modifications, and any spawned child processes.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Inspect the host for suspicious or abnormal behavior in the alert timeframe.
- Create a memory dump of the child process for analysis.

### 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.
- Remove and block malicious artifacts identified during triage.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- 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.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- 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 queryedit

sequence by host.id with maxspan=1m [process where event.code == "1"
and /* sysmon process creation */ process.parent.name :
("winword.exe", "excel.exe", "outlook.exe", "powerpnt.exe",
"eqnedt32.exe", "fltldr.exe", "mspub.exe",
"msaccess.exe","cscript.exe", "wscript.exe", "rundll32.exe",
"regsvr32.exe", "mshta.exe", "wmic.exe",
"cmstp.exe", "msxsl.exe") and /* noisy FP patterns */ not
(process.parent.name : "EXCEL.EXE" and process.executable :
"?:\\Program Files\\Microsoft Office\\root\\Office*\\ADDINS\\*.exe")
and not (process.executable : "?:\\Windows\\splwow64.exe" and
process.args in ("8192", "12288") and process.parent.name :
("winword.exe", "excel.exe", "outlook.exe", "powerpnt.exe")) and
not (process.parent.name : "rundll32.exe" and process.parent.args : ("
?:\\WINDOWS\\Installer\\MSI*.tmp,zzzzInvokeManagedCustomActionOutOfPro
c", "--no-sandbox")) and not (process.executable :
("?:\\Program Files
(x86)\\Microsoft\\EdgeWebView\\Application\\*\\msedgewebview2.exe",
"?:\\Program Files\\Adobe\\Acrobat DC\\Acrobat\\Acrobat.exe",
"?:\\Windows\\SysWOW64\\DWWIN.EXE") and process.parent.name :
("winword.exe", "excel.exe", "outlook.exe", "powerpnt.exe")) and
not (process.parent.name : "regsvr32.exe" and process.parent.args :
("?:\\Program Files\\*", "?:\\Program Files (x86)\\*")) ] by
process.parent.entity_id, process.entity_id [process where
event.code == "10" and /* Sysmon process access event from unknown
module */ winlog.event_data.CallTrace : "*UNKNOWN*"] by
process.entity_id, winlog.event_data.TargetProcessGUID

Threat mappingedit

Framework: MITRE ATT&CKTM

Rule version historyedit

Version 102 (8.6.0 release)
  • Formatting only
Version 101 (8.5.0 release)
  • Formatting only
Version 4 (8.4.0 release)
  • Updated query, changed from:

    sequence by host.id with maxspan=1m [process where event.code == "1"
    and /* sysmon process creation */ process.parent.name :
    ("winword.exe", "excel.exe", "outlook.exe", "powerpnt.exe",
    "eqnedt32.exe", "fltldr.exe", "mspub.exe",
    "msaccess.exe", "powershell.exe", "pwsh.exe",
    "cscript.exe", "wscript.exe", "rundll32.exe", "regsvr32.exe",
    "mshta.exe", "wmic.exe", "cmstp.exe",
    "msxsl.exe")] by process.parent.entity_id, process.entity_id
    [process where event.code == "10" and /* Sysmon process access
    event from unknown module */ winlog.event_data.CallTrace :
    "*UNKNOWN*"] by process.entity_id, winlog.event_data.TargetProcessGUID
Version 2 (8.2.0 release)
  • Formatting only