Suspicious Zoom Child Process

  1[metadata]
  2creation_date = "2020/09/03"
  3integration = ["endpoint", "windows", "sentinel_one_cloud_funnel", "m365_defender", "system", "crowdstrike"]
  4maturity = "production"
  5updated_date = "2025/03/20"
  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 = """
 36A suspicious Zoom child process was detected, which may indicate an attempt to run unnoticed. Verify process details
 37such as command line, network connections, file writes and associated file signature details as well.
 38"""
 39from = "now-9m"
 40index = [
 41    "endgame-*",
 42    "logs-crowdstrike.fdr*",
 43    "logs-endpoint.events.process-*",
 44    "logs-m365_defender.event-*",
 45    "logs-sentinel_one_cloud_funnel.*",
 46    "logs-system.security*",
 47    "logs-windows.forwarded*",
 48    "logs-windows.sysmon_operational-*",
 49    "winlogbeat-*",
 50]
 51language = "eql"
 52license = "Elastic License v2"
 53name = "Suspicious Zoom Child Process"
 54note = """## Triage and analysis
 55
 56### Investigating Suspicious Zoom Child Process
 57
 58By examining the specific traits of Windows binaries -- such as process trees, command lines, network connections, registry modifications, and so on -- it's possible to establish a baseline of normal activity. Deviations from this baseline can indicate malicious activity, such as masquerading, and deserve further investigation.
 59
 60This rule identifies a potential malicious process masquerading as `Zoom.exe` or exploiting a vulnerability in the application causing it to execute code.
 61
 62> **Note**:
 63> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/current/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 64
 65#### Possible investigation steps
 66
 67- 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.
 68- Investigate other alerts associated with the user/host during the past 48 hours.
 69- Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
 70- Examine the command line of the child process to determine which commands or scripts were executed.
 71- Examine the host for derived artifacts that indicate suspicious activities:
 72  - Analyze the process executable using a private sandboxed analysis system.
 73  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 74    - Attempts to contact external domains and addresses.
 75      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 76      - Examine the DNS cache for suspicious or anomalous entries.
 77        - $osquery_0
 78    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 79    - Examine the host services for suspicious or anomalous entries.
 80      - $osquery_1
 81      - $osquery_2
 82      - $osquery_3
 83  - 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.
 84- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
 85
 86
 87### False positive analysis
 88
 89- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
 90
 91### Response and remediation
 92
 93- Initiate the incident response process based on the outcome of the triage.
 94- Isolate the involved host to prevent further post-compromise behavior.
 95- If the triage identified malware, search the environment for additional compromised hosts.
 96  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 97  - Stop suspicious processes.
 98  - Immediately block the identified indicators of compromise (IoCs).
 99  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
100- Remove and block malicious artifacts identified during triage.
101- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
102- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
103- 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).
104"""
105risk_score = 47
106rule_id = "97aba1ef-6034-4bd3-8c1a-1e0996b27afa"
107severity = "medium"
108tags = [
109    "Domain: Endpoint",
110    "OS: Windows",
111    "Use Case: Threat Detection",
112    "Tactic: Defense Evasion",
113    "Tactic: Execution",
114    "Data Source: Elastic Endgame",
115    "Resources: Investigation Guide",
116    "Data Source: Elastic Defend",
117    "Data Source: SentinelOne",
118    "Data Source: Microsoft Defender for Endpoint",
119    "Data Source: Windows Security Event Logs",
120    "Data Source: Crowdstrike",
121    "Data Source: Sysmon",
122]
123timestamp_override = "event.ingested"
124type = "eql"
125
126query = '''
127process where host.os.type == "windows" and event.type == "start" and
128 process.parent.name : "Zoom.exe" and process.name : ("cmd.exe", "powershell.exe", "pwsh.exe", "powershell_ise.exe")
129'''
130
131
132[[rule.threat]]
133framework = "MITRE ATT&CK"
134[[rule.threat.technique]]
135id = "T1036"
136name = "Masquerading"
137reference = "https://attack.mitre.org/techniques/T1036/"
138
139[[rule.threat.technique]]
140id = "T1055"
141name = "Process Injection"
142reference = "https://attack.mitre.org/techniques/T1055/"
143
144
145[rule.threat.tactic]
146id = "TA0005"
147name = "Defense Evasion"
148reference = "https://attack.mitre.org/tactics/TA0005/"
149[[rule.threat]]
150framework = "MITRE ATT&CK"
151[[rule.threat.technique]]
152id = "T1203"
153name = "Exploitation for Client Execution"
154reference = "https://attack.mitre.org/techniques/T1203/"
155
156
157[rule.threat.tactic]
158id = "TA0002"
159name = "Execution"
160reference = "https://attack.mitre.org/tactics/TA0002/"