Suspicious Communication App Child Process

  1[metadata]
  2creation_date = "2023/08/04"
  3integration = ["endpoint", "sentinel_one_cloud_funnel"]
  4maturity = "production"
  5updated_date = "2026/09/18"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies suspicious child processes of communications apps, which can indicate a potential masquerading as the
 11communication app or the exploitation of a vulnerability on the application causing it to execute code.
 12"""
 13from = "now-9m"
 14index = ["logs-endpoint.events.process-*", "logs-sentinel_one_cloud_funnel.*", "endgame-*"]
 15language = "eql"
 16license = "Elastic License v2"
 17name = "Suspicious Communication App Child Process"
 18risk_score = 47
 19rule_id = "adbfa3ee-777e-4747-b6b0-7bd645f30880"
 20severity = "medium"
 21tags = [
 22    "Domain: Endpoint",
 23    "OS: Windows",
 24    "Use Case: Threat Detection",
 25    "Tactic: Defense Evasion",
 26    "Tactic: Persistence",
 27    "Data Source: Elastic Defend",
 28    "Resources: Investigation Guide",
 29    "Data Source: SentinelOne",
 30    "Data Source: Elastic Endgame",
 31    "Noise: Medium",
 32    "Performance: Normal",
 33    "Rule Type: Event Correlation (EQL)",
 34    "Platform: Windows",
 35]
 36timestamp_override = "event.ingested"
 37type = "eql"
 38
 39query = '''
 40process where host.os.type == "windows" and event.type == "start" and
 41  process.parent.name : (
 42    "slack.exe", "CiscoCollabHost.exe", "WebexHost.exe", "Teams.exe",
 43    "Discord.exe", "Whatsapp.exe", "Zoom.exe", "thunderbird.exe"
 44  ) and
 45  not process.executable : (
 46              "?:\\Program Files\\*.exe", 
 47              "?:\\Program Files (x86)\\*.exe", 
 48              "?:\\Windows\\System32\\WerFault.exe", 
 49              "?:\\Windows\\SysWOW64\\WerFault.exe"
 50  ) and
 51
 52  /* Common Signed Browser Processes */
 53  not (
 54    process.executable : (
 55        "?:\\Users\\*\\AppData\\Local\\Google\\Chrome\\Application\\chrome.exe",
 56        "?:\\Users\\*\\AppData\\Local\\Island\\Island\\Application\\Island.exe",
 57        "?:\\Users\\*\\AppData\\Local\\Mozilla Firefox\\firefox.exe",
 58        "?:\\Users\\*\\AppData\\Local\\Programs\\Opera\\opera.exe"
 59    ) and process.code_signature.trusted == true
 60  ) and
 61  (
 62    /* Slack */
 63    (process.parent.name : "slack.exe" and not
 64      (
 65        (
 66          process.executable : (
 67            "?:\\Users\\*\\AppData\\Roaming\\Zoom\\bin*\\Zoom.exe",
 68            "?:\\Windows\\System32\\rundll32.exe",
 69            "?:\\Windows\\System32\\notepad.exe"
 70          ) and process.code_signature.trusted == true
 71        ) or
 72        (
 73          process.code_signature.subject_name : (
 74            "Slack Technologies, Inc.",
 75            "Slack Technologies, LLC"
 76          ) and process.code_signature.trusted == true
 77        ) or
 78        (
 79          (process.name : "powershell.exe" and process.command_line : "powershell.exe -c Invoke-WebRequest -Uri https://slackb.com/*") or
 80          (process.name : "cmd.exe" and process.command_line : "C:\\WINDOWS\\system32\\cmd.exe /d /s /c \"%windir%\\System32\\rundll32.exe User32.dll,SetFocus 0\"")
 81        )
 82      )
 83    ) or
 84
 85    /* WebEx */
 86    (process.parent.name : ("CiscoCollabHost.exe", "WebexHost.exe") and not
 87      (
 88        process.code_signature.subject_name : (
 89          "Cisco Systems, Inc.",
 90          "Cisco WebEx LLC",
 91          "Cisco Systems Inc."
 92        ) and process.code_signature.trusted == true
 93      )
 94    ) or
 95
 96    /* Teams */
 97    (process.parent.name : "Teams.exe" and not
 98      (
 99        (
100          process.executable : (
101            "?:\\Windows\\BrowserCore\\BrowserCore.exe",
102            "?:\\Users\\*\\AppData\\Local\\Microsoft\\Teams\\current\\Teams.exe"
103          ) and process.code_signature.trusted == true
104        ) or
105        (
106          process.code_signature.subject_name : (
107            "Microsoft Corporation",
108            "Microsoft 3rd Party Application Component"
109          ) and process.code_signature.trusted == true
110        ) or
111        (
112          (process.name : "taskkill.exe" and process.args : "Teams.exe")
113        )
114      )
115    ) or
116
117    /* Discord */
118    (process.parent.name : "Discord.exe" and not
119      (
120        (
121          process.executable : (
122            "?:\\Windows\\System32\\reg.exe",
123            "?:\\Windows\\SysWOW64\\reg.exe"
124          ) and process.code_signature.trusted == true
125        ) or
126        (
127          process.code_signature.subject_name : (
128            "Discord Inc."
129          ) and process.code_signature.trusted == true
130        ) or
131        (
132          process.name : "cmd.exe" and
133          (
134            process.command_line : (
135              "C:\\WINDOWS\\system32\\cmd.exe /d /s /c \"chcp\"",
136              "C:\\WINDOWS\\system32\\cmd.exe /q /d /s /c \"C:\\Program^ Files\\NVIDIA^ Corporation\\NVSMI\\nvidia-smi.exe\""
137            ) or
138            process.args : (
139              "C:\\WINDOWS/System32/nvidia-smi.exe",
140              "C:\\WINDOWS\\System32\\nvidia-smi.exe",
141              "C:\\Windows\\System32\\DriverStore\\FileRepository/*/nvidia-smi.exe*"
142            )
143          )
144        )
145      )
146    ) or
147
148    /* WhatsApp */
149    (process.parent.name : "Whatsapp.exe" and not
150      (
151        (
152          process.executable : (
153            "?:\\Windows\\System32\\reg.exe",
154            "?:\\Windows\\SysWOW64\\reg.exe"
155          ) and process.code_signature.trusted == true
156        ) or
157        (
158          process.code_signature.subject_name : (
159            "WhatsApp LLC",
160            "WhatsApp, Inc",
161            "24803D75-212C-471A-BC57-9EF86AB91435"
162          ) and process.code_signature.trusted == true
163        ) or
164        (
165          (process.name : "cmd.exe" and process.command_line : "C:\\Windows\\system32\\cmd.exe /d /s /c \"C:\\Windows\\system32\\wbem\\wmic.exe*")
166        )
167      )
168    ) or
169
170    /* Zoom */
171    (process.parent.name : "Zoom.exe" and not
172      (
173        (
174          process.executable : (
175            "?:\\Users\\*\\AppData\\Local\\BraveSoftware\\Brave-Browser\\Application\\brave.exe"
176          ) and process.code_signature.trusted == true
177        ) or
178        (
179          process.code_signature.subject_name : (
180            "Zoom Video Communications, Inc.",
181            "Zoom Communications, Inc."
182          ) and process.code_signature.trusted == true
183        )
184      )
185    ) or
186
187    /* Thunderbird */
188    (process.parent.name : "thunderbird.exe" and not
189      (
190        (
191          process.executable : (
192            "?:\\Windows\\splwow64.exe", 
193            "?:\\Windows\\System32\\spool\\drivers\\x64\\3\\*.EXE"
194          ) and process.code_signature.trusted == true
195        ) or
196        (
197          process.code_signature.subject_name : (
198            "Mozilla Corporation"
199          ) and process.code_signature.trusted == true
200        )
201      )
202    )
203  )
204'''
205
206setup = """## Setup
207
208This rule is designed for data generated by [Elastic Defend](https://www.elastic.co/security/endpoint-security), which provides native endpoint detection and response, along with event enrichments designed to work with our detection rules.
209
210Setup instructions: https://ela.st/install-elastic-defend
211
212### Additional data sources
213
214This rule also supports the following third-party data sources. For setup instructions, refer to the links below:
215
216- [SentinelOne Cloud Funnel](https://ela.st/sentinel-one-cloud-funnel)
217"""
218
219note = """## Triage and analysis
220
221> **Disclaimer**:
222> This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.
223
224### Investigating Suspicious Communication App Child Process
225
226Communication apps like Slack, WebEx, and Teams are integral to modern workflows, facilitating collaboration. However, adversaries can exploit these apps by spawning unauthorized child processes, potentially masquerading as legitimate ones or exploiting vulnerabilities to execute malicious code. The detection rule identifies such anomalies by monitoring child processes of these apps, ensuring they are trusted and signed by recognized entities. This helps in identifying potential threats that deviate from expected behavior, thus safeguarding against unauthorized access and execution.
227
228### Possible investigation steps
229
230- Review the process details, including the parent process name and executable path, to confirm if the child process is expected or unusual for the communication app in question.
231- Check the code signature of the suspicious child process to determine if it is trusted and signed by a recognized entity, as specified in the query.
232- Investigate the command line arguments of the child process to identify any potentially malicious or unexpected commands being executed.
233- Correlate the event with other logs or alerts to identify any related suspicious activities or patterns, such as repeated unauthorized child process executions.
234- Assess the user account associated with the process to determine if it has been compromised or is exhibiting unusual behavior.
235- Examine the network activity of the affected system to identify any suspicious outbound connections that may indicate data exfiltration or communication with a command and control server.
236
237### False positive analysis
238
239- Legitimate software updates or installations may trigger the rule if they spawn child processes from communication apps. Users can create exceptions for known update processes by verifying their code signatures and paths.
240- Custom scripts or automation tools that interact with communication apps might be flagged. Users should ensure these scripts are signed and located in trusted directories, then add them to the exception list.
241- Certain administrative tasks, such as using command-line tools like cmd.exe or powershell.exe, may be mistakenly identified as suspicious. Users can whitelist specific command lines or arguments that are regularly used in their environment.
242- Some third-party integrations with communication apps may generate child processes that are not inherently malicious. Users should verify the legitimacy of these integrations and add them to the trusted list if they are deemed safe.
243- Regularly review and update the list of trusted code signatures and executable paths to ensure that legitimate processes are not inadvertently flagged as suspicious.
244
245### Response and remediation
246
247- Immediately isolate the affected system from the network to prevent further unauthorized access or execution of malicious code.
248- Terminate any suspicious child processes identified by the detection rule that are not signed by recognized entities or are executing from unexpected locations.
249- Conduct a thorough review of the affected communication app's logs and configurations to identify any unauthorized changes or access patterns.
250- Restore the affected system from a known good backup if malicious activity is confirmed, ensuring that the backup is free from compromise.
251- Update the communication app and all related software to the latest versions to patch any known vulnerabilities that may have been exploited.
252- Implement application whitelisting to ensure only trusted and signed applications can execute, reducing the risk of similar threats.
253- Escalate the incident to the security operations center (SOC) or relevant security team for further investigation and to assess the potential impact on other systems."""
254
255
256[[rule.threat]]
257framework = "MITRE ATT&CK"
258
259[[rule.threat.technique]]
260id = "T1036"
261name = "Masquerading"
262reference = "https://attack.mitre.org/techniques/T1036/"
263
264[[rule.threat.technique.subtechnique]]
265id = "T1036.001"
266name = "Invalid Code Signature"
267reference = "https://attack.mitre.org/techniques/T1036/001/"
268
269[[rule.threat.technique.subtechnique]]
270id = "T1036.005"
271name = "Match Legitimate Resource Name or Location"
272reference = "https://attack.mitre.org/techniques/T1036/005/"
273
274[[rule.threat.technique]]
275id = "T1055"
276name = "Process Injection"
277reference = "https://attack.mitre.org/techniques/T1055/"
278
279[rule.threat.tactic]
280id = "TA0005"
281name = "Defense Evasion"
282reference = "https://attack.mitre.org/tactics/TA0005/"
283
284[[rule.threat]]
285framework = "MITRE ATT&CK"
286
287[[rule.threat.technique]]
288id = "T1554"
289name = "Compromise Host Software Binary"
290reference = "https://attack.mitre.org/techniques/T1554/"
291
292[rule.threat.tactic]
293id = "TA0003"
294name = "Persistence"
295reference = "https://attack.mitre.org/tactics/TA0003/"
296
297[[rule.threat]]
298framework = "MITRE ATT&CK"
299
300[[rule.threat.technique]]
301id = "T1203"
302name = "Exploitation for Client Execution"
303reference = "https://attack.mitre.org/techniques/T1203/"
304
305[rule.threat.tactic]
306id = "TA0002"
307name = "Execution"
308reference = "https://attack.mitre.org/tactics/TA0002/"