Startup Folder Persistence via Unsigned Process

  1[metadata]
  2creation_date = "2020/11/29"
  3integration = ["endpoint"]
  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 files written or modified in the startup folder by unsigned processes. Adversaries may abuse this technique
 37to maintain persistence in an environment.
 38"""
 39from = "now-9m"
 40index = ["logs-endpoint.events.process-*", "logs-endpoint.events.file-*"]
 41language = "eql"
 42license = "Elastic License v2"
 43name = "Startup Folder Persistence via Unsigned Process"
 44note = """## Triage and analysis
 45
 46### Investigating Startup Folder Persistence via Unsigned Process
 47
 48The Windows Startup folder is a special folder in Windows. Programs added to this folder are executed during account logon, without user interaction, providing an excellent way for attackers to maintain persistence.
 49
 50This rule looks for unsigned processes writing to the Startup folder locations.
 51
 52> **Note**:
 53> 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.
 54
 55#### Possible investigation steps
 56
 57- 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.
 58- Investigate other alerts associated with the user/host during the past 48 hours.
 59- Validate if the activity is not related to planned patches, updates, network administrator activity, or legitimate software installations.
 60- Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
 61- Examine the host for derived artifacts that indicate suspicious activities:
 62  - Analyze the file using a private sandboxed analysis system.
 63  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 64    - Attempts to contact external domains and addresses.
 65      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 66      - Examine the DNS cache for suspicious or anomalous entries.
 67        - $osquery_0
 68    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 69    - Examine the host services for suspicious or anomalous entries.
 70      - $osquery_1
 71      - $osquery_2
 72      - $osquery_3
 73  - 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.
 74- Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
 75
 76### False positive analysis
 77
 78- There is a high possibility of benign legitimate programs being added to Startup folders. This activity could be based on new software installations, patches, or any kind of network administrator related activity. Before undertaking further investigation, verify that this activity is not benign.
 79
 80### Related rules
 81
 82- Suspicious Startup Shell Folder Modification - c8b150f0-0164-475b-a75e-74b47800a9ff
 83- Persistent Scripts in the Startup Directory - f7c4dc5a-a58d-491d-9f14-9b66507121c0
 84
 85### Response and remediation
 86
 87- Initiate the incident response process based on the outcome of the triage.
 88- Isolate the involved host to prevent further post-compromise behavior.
 89- If the triage identified malware, search the environment for additional compromised hosts.
 90  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 91  - Stop suspicious processes.
 92  - Immediately block the identified indicators of compromise (IoCs).
 93  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 94- Remove and block malicious artifacts identified during triage.
 95- 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.
 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"""
100risk_score = 47
101rule_id = "2fba96c0-ade5-4bce-b92f-a5df2509da3f"
102severity = "medium"
103tags = [
104    "Domain: Endpoint",
105    "OS: Windows",
106    "Use Case: Threat Detection",
107    "Tactic: Persistence",
108    "Tactic: Defense Evasion",
109    "Resources: Investigation Guide",
110    "Data Source: Elastic Defend",
111]
112type = "eql"
113
114query = '''
115sequence by host.id, process.entity_id with maxspan=5s
116  [process where host.os.type == "windows" and event.type == "start" and process.code_signature.trusted == false and
117  /* suspicious paths can be added here  */
118   process.executable : ("C:\\Users\\*.exe",
119                         "C:\\ProgramData\\*.exe",
120                         "C:\\Windows\\Temp\\*.exe",
121                         "C:\\Windows\\Tasks\\*.exe",
122                         "C:\\Intel\\*.exe",
123                         "C:\\PerfLogs\\*.exe")
124   ]
125   [file where host.os.type == "windows" and event.type != "deletion" and user.domain != "NT AUTHORITY" and
126    file.path : ("C:\\Users\\*\\AppData\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\*",
127                 "C:\\ProgramData\\Microsoft\\Windows\\Start Menu\\Programs\\StartUp\\*")
128   ]
129'''
130
131
132[[rule.threat]]
133framework = "MITRE ATT&CK"
134[[rule.threat.technique]]
135id = "T1547"
136name = "Boot or Logon Autostart Execution"
137reference = "https://attack.mitre.org/techniques/T1547/"
138[[rule.threat.technique.subtechnique]]
139id = "T1547.001"
140name = "Registry Run Keys / Startup Folder"
141reference = "https://attack.mitre.org/techniques/T1547/001/"
142
143
144
145[rule.threat.tactic]
146id = "TA0003"
147name = "Persistence"
148reference = "https://attack.mitre.org/tactics/TA0003/"
149[[rule.threat]]
150framework = "MITRE ATT&CK"
151[[rule.threat.technique]]
152id = "T1036"
153name = "Masquerading"
154reference = "https://attack.mitre.org/techniques/T1036/"
155[[rule.threat.technique.subtechnique]]
156id = "T1036.001"
157name = "Invalid Code Signature"
158reference = "https://attack.mitre.org/techniques/T1036/001/"
159
160
161
162[rule.threat.tactic]
163id = "TA0005"
164name = "Defense Evasion"
165reference = "https://attack.mitre.org/tactics/TA0005/"