Unusual Parent-Child Relationship
Identifies Windows programs run from unexpected parent processes. This could indicate masquerading or other strange activity on a system.
Elastic rule (View on GitHub)
1[metadata]
2creation_date = "2020/02/18"
3integration = ["endpoint", "windows", "system"]
4maturity = "production"
5updated_date = "2024/05/21"
6
7[transform]
8[[transform.osquery]]
9label = "Osquery - Retrieve DNS Cache"
10query = "SELECT * FROM dns_cache"
11
12[[transform.osquery]]
13label = "Osquery - Retrieve All Services"
14query = "SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services"
15
16[[transform.osquery]]
17label = "Osquery - Retrieve Services Running on User Accounts"
18query = """
19SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE
20NOT (user_account LIKE '%LocalSystem' OR user_account LIKE '%LocalService' OR user_account LIKE '%NetworkService' OR
21user_account == null)
22"""
23
24[[transform.osquery]]
25label = "Osquery - Retrieve Service Unsigned Executables with Virustotal Link"
26query = """
27SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid,
28services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path =
29authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != 'trusted'
30"""
31
32
33[rule]
34author = ["Elastic"]
35description = """
36Identifies Windows programs run from unexpected parent processes. This could indicate masquerading or other strange
37activity on a system.
38"""
39from = "now-9m"
40index = [
41 "winlogbeat-*",
42 "logs-endpoint.events.process-*",
43 "logs-windows.*",
44 "endgame-*",
45 "logs-system.security*",
46]
47language = "eql"
48license = "Elastic License v2"
49name = "Unusual Parent-Child Relationship"
50note = """## Triage and analysis
51
52### Investigating Unusual Parent-Child Relationship
53
54Windows internal/system processes have some characteristics that can be used to spot suspicious activities. One of these characteristics is parent-child relationships. These relationships can be used to baseline the typical behavior of the system and then alert on occurrences that don't comply with the baseline.
55
56This rule uses this information to spot suspicious parent and child processes.
57
58> **Note**:
59> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
60
61#### Possible investigation steps
62
63- 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.
64- Investigate other alerts associated with the user/host during the past 48 hours.
65- Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
66- Examine the host for derived artifacts that indicate suspicious activities:
67 - Analyze the process executable using a private sandboxed analysis system.
68 - Observe and collect information about the following activities in both the sandbox and the alert subject host:
69 - Attempts to contact external domains and addresses.
70 - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
71 - Examine the DNS cache for suspicious or anomalous entries.
72 - $osquery_0
73 - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
74 - Examine the host services for suspicious or anomalous entries.
75 - $osquery_1
76 - $osquery_2
77 - $osquery_3
78 - Retrieve the files' SHA-256 hash values using the PowerShell `Get-FileHash` cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
79- Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
80
81
82### False positive analysis
83
84- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
85
86### Response and remediation
87
88- Initiate the incident response process based on the outcome of the triage.
89- Isolate the involved host to prevent further post-compromise behavior.
90- If the triage identified malware, search the environment for additional compromised hosts.
91 - Implement temporary network rules, procedures, and segmentation to contain the malware.
92 - Stop suspicious processes.
93 - Immediately block the identified indicators of compromise (IoCs).
94 - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
95- Remove and block malicious artifacts identified during triage.
96- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
97- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
98- 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).
99"""
100references = [
101 "https://github.com/sbousseaden/Slides/blob/master/Hunting%20MindMaps/PNG/Windows%20Processes%20TH.map.png",
102 "https://www.andreafortuna.org/2017/06/15/standard-windows-processes-a-brief-reference/",
103]
104risk_score = 47
105rule_id = "35df0dd8-092d-4a83-88c1-5151a804f31b"
106setup = """## Setup
107
108If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
109events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
110Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
111`event.ingested` to @timestamp.
112For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
113"""
114severity = "medium"
115tags = [
116 "Domain: Endpoint",
117 "OS: Windows",
118 "Use Case: Threat Detection",
119 "Tactic: Privilege Escalation",
120 "Resources: Investigation Guide",
121 "Data Source: Elastic Endgame",
122 "Data Source: Elastic Defend",
123]
124timestamp_override = "event.ingested"
125type = "eql"
126
127query = '''
128process where host.os.type == "windows" and event.type == "start" and
129process.parent.name != null and
130 (
131 /* suspicious parent processes */
132 (process.name:"autochk.exe" and not process.parent.name:"smss.exe") or
133 (process.name:("fontdrvhost.exe", "dwm.exe") and not process.parent.name:("wininit.exe", "winlogon.exe")) or
134 (process.name:("consent.exe", "RuntimeBroker.exe", "TiWorker.exe") and not process.parent.name:"svchost.exe") or
135 (process.name:"SearchIndexer.exe" and not process.parent.name:"services.exe") or
136 (process.name:"SearchProtocolHost.exe" and not process.parent.name:("SearchIndexer.exe", "dllhost.exe")) or
137 (process.name:"dllhost.exe" and not process.parent.name:("services.exe", "svchost.exe")) or
138 (process.name:"smss.exe" and not process.parent.name:("System", "smss.exe")) or
139 (process.name:"csrss.exe" and not process.parent.name:("smss.exe", "svchost.exe")) or
140 (process.name:"wininit.exe" and not process.parent.name:"smss.exe") or
141 (process.name:"winlogon.exe" and not process.parent.name:"smss.exe") or
142 (process.name:("lsass.exe", "LsaIso.exe") and not process.parent.name:"wininit.exe") or
143 (process.name:"LogonUI.exe" and not process.parent.name:("wininit.exe", "winlogon.exe")) or
144 (process.name:"services.exe" and not process.parent.name:"wininit.exe") or
145 (process.name:"svchost.exe" and not process.parent.name:("MsMpEng.exe", "services.exe", "svchost.exe")) or
146 (process.name:"spoolsv.exe" and not process.parent.name:"services.exe") or
147 (process.name:"taskhost.exe" and not process.parent.name:("services.exe", "svchost.exe", "ngentask.exe")) or
148 (process.name:"taskhostw.exe" and not process.parent.name:("services.exe", "svchost.exe")) or
149 (process.name:"userinit.exe" and not process.parent.name:("dwm.exe", "winlogon.exe")) or
150 (process.name:("wmiprvse.exe", "wsmprovhost.exe", "winrshost.exe") and not process.parent.name:"svchost.exe") or
151 /* suspicious child processes */
152 (process.parent.name:("SearchProtocolHost.exe", "taskhost.exe", "csrss.exe") and not process.name:("werfault.exe", "wermgr.exe", "WerFaultSecure.exe", "conhost.exe")) or
153 (process.parent.name:"autochk.exe" and not process.name:("chkdsk.exe", "doskey.exe", "WerFault.exe")) or
154 (process.parent.name:"smss.exe" and not process.name:("autochk.exe", "smss.exe", "csrss.exe", "wininit.exe", "winlogon.exe", "setupcl.exe", "WerFault.exe")) or
155 (process.parent.name:"wermgr.exe" and not process.name:("WerFaultSecure.exe", "wermgr.exe", "WerFault.exe")) or
156 (process.parent.name:"conhost.exe" and not process.name:("mscorsvw.exe", "wermgr.exe", "WerFault.exe", "WerFaultSecure.exe"))
157 )
158'''
159
160
161[[rule.threat]]
162framework = "MITRE ATT&CK"
163[[rule.threat.technique]]
164id = "T1055"
165name = "Process Injection"
166reference = "https://attack.mitre.org/techniques/T1055/"
167[[rule.threat.technique.subtechnique]]
168id = "T1055.012"
169name = "Process Hollowing"
170reference = "https://attack.mitre.org/techniques/T1055/012/"
171
172
173
174[rule.threat.tactic]
175id = "TA0004"
176name = "Privilege Escalation"
177reference = "https://attack.mitre.org/tactics/TA0004/"
Triage and analysis
Investigating Unusual Parent-Child Relationship
Windows internal/system processes have some characteristics that can be used to spot suspicious activities. One of these characteristics is parent-child relationships. These relationships can be used to baseline the typical behavior of the system and then alert on occurrences that don't comply with the baseline.
This rule uses this information to spot suspicious parent and child processes.
Note: This investigation guide uses the Osquery Markdown Plugin introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
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.
- Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
- Examine the host for derived artifacts that indicate suspicious activities:
- Analyze the process executable using a private sandboxed analysis system.
- Observe and collect information about the following activities in both the sandbox and the alert subject host:
- Attempts to contact external domains and addresses.
- Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process'
process.entity_id
. - Examine the DNS cache for suspicious or anomalous entries.
- $osquery_0
- Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process'
- Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
- Examine the host services for suspicious or anomalous entries.
- $osquery_1
- $osquery_2
- $osquery_3
- Attempts to contact external domains and addresses.
- Retrieve the files' SHA-256 hash values using the PowerShell
Get-FileHash
cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
- Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
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.
- 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 antimalware scan. This may 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.
- 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).
References
Related rules
- Component Object Model Hijacking
- Conhost Spawned By Suspicious Parent Process
- Disabling User Account Control via Registry Modification
- Persistence via Update Orchestrator Service Hijack
- Privilege Escalation via Named Pipe Impersonation