Potential Persistence Through init.d Detected

  1[metadata]
  2creation_date = "2023/03/21"
  3integration = ["endpoint"]
  4maturity = "production"
  5min_stack_comments = "Multiple field support in the New Terms rule type was added in Elastic 8.6"
  6min_stack_version = "8.6.0"
  7updated_date = "2023/08/21"
  8
  9[transform]
 10[[transform.osquery]]
 11label = "Osquery - Retrieve File Information"
 12query = "SELECT * FROM file WHERE path = {{file.path}}"
 13
 14[[transform.osquery]]
 15label = "Osquery - Retrieve File Listing Information"
 16query = "SELECT * FROM file WHERE (path LIKE '/etc/init.d/%' OR path LIKE '/run/systemd/generator.late/%')"
 17
 18[[transform.osquery]]
 19label = "Osquery - Retrieve Additional File Listing Information"
 20query = """
 21SELECT
 22  f.path,
 23  u.username AS file_owner,
 24  g.groupname AS group_owner,
 25  datetime(f.atime, 'unixepoch') AS file_last_access_time,
 26  datetime(f.mtime, 'unixepoch') AS file_last_modified_time,
 27  datetime(f.ctime, 'unixepoch') AS file_last_status_change_time,
 28  datetime(f.btime, 'unixepoch') AS file_created_time,
 29  f.size AS size_bytes
 30FROM
 31  file f
 32  LEFT JOIN users u ON f.uid = u.uid
 33  LEFT JOIN groups g ON f.gid = g.gid
 34WHERE (path LIKE '/etc/init.d/%' OR path LIKE '/run/systemd/generator.late/%')
 35"""
 36
 37[[transform.osquery]]
 38label = "Osquery - Retrieve Running Processes by User"
 39query = "SELECT pid, username, name FROM processes p JOIN users u ON u.uid = p.uid ORDER BY username"
 40
 41[[transform.osquery]]
 42label = "Osquery - Retrieve Crontab Information"
 43query = "SELECT * FROM crontab"
 44
 45[rule]
 46author = ["Elastic"]
 47description = """
 48Files that are placed in the /etc/init.d/ directory in Unix can be used to start custom applications, services, scripts
 49or commands during start-up. Init.d has been mostly replaced in favor of Systemd. However, the 
 50"systemd-sysv-generator" can convert init.d files to service unit files that run at boot. Adversaries may add or 
 51alter files located in the /etc/init.d/ directory to execute malicious code upon boot in order to gain persistence 
 52on the system. 
 53"""
 54from = "now-9m"
 55index = ["logs-endpoint.events.*", "endgame-*"]
 56language = "kuery"
 57license = "Elastic License v2"
 58name = "Potential Persistence Through init.d Detected"
 59note = """## Triage and analysis
 60
 61### Investigating Potential Persistence Through init.d Detected
 62
 63The `/etc/init.d` directory is used in Linux systems to store the initialization scripts for various services and daemons that are executed during system startup and shutdown.
 64
 65Attackers can abuse files within the `/etc/init.d/` directory to run scripts, commands or malicious software every time a system is rebooted by converting an executable file into a service file through the `systemd-sysv-generator`. After conversion, a unit file is created within the `/run/systemd/generator.late/` directory.
 66
 67This rule looks for the creation of new files within the `/etc/init.d/` directory. Executable files in these directories will automatically run at boot with root privileges.
 68
 69> **Note**:
 70> 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.
 71> This investigation guide uses [placeholder fields](https://www.elastic.co/guide/en/security/current/osquery-placeholder-fields.html) to dynamically pass alert data into Osquery queries. Placeholder fields were introduced in Elastic Stack version 8.7.0. If you're using Elastic Stack version 8.6.0 or earlier, you'll need to manually adjust this investigation guide's queries to ensure they properly run.
 72#### Possible Investigation Steps
 73
 74- Investigate the file that was created or modified.
 75  - $osquery_0
 76- Investigate whether any other files in the `/etc/init.d/` or `/run/systemd/generator.late/` directories have been altered.
 77  - $osquery_1
 78  - $osquery_2
 79- Investigate the script execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence and whether they are located in expected locations.
 80  - $osquery_3
 81- Investigate syslog through the `sudo cat /var/log/syslog | grep 'LSB'` command to find traces of the LSB header of the script (if present). If syslog is being ingested into Elasticsearch, the same can be accomplished through Kibana.
 82- Investigate other alerts associated with the user/host during the past 48 hours.
 83- Validate whether this activity is related to planned patches, updates, network administrator activity, or legitimate software installations.
 84- Investigate whether the altered scripts call other malicious scripts elsewhere on the file system. 
 85  - If scripts or executables were dropped, retrieve the files and determine if they are malicious:
 86    - Use a private sandboxed malware analysis system to perform analysis.
 87      - Observe and collect information about the following activities:
 88        - Attempts to contact external domains and addresses.
 89          - Check if the domain is newly registered or unexpected.
 90          - Check the reputation of the domain or IP address.
 91        - File access, modification, and creation activities.
 92        - Cron jobs, services and other persistence mechanisms.
 93            - $osquery_4
 94
 95### False Positive Analysis
 96
 97- If this activity is related to new benign software installation activity, consider adding exceptions — preferably with a combination of user and command line conditions.
 98- If this activity is related to a system administrator who uses init.d for administrative purposes, consider adding exceptions for this specific administrator user account. 
 99- Try to understand the context of the execution by thinking about the user, machine, or business purpose. A small number of endpoints, such as servers with unique software, might appear unusual but satisfy a specific business need.
100
101### Related Rules
102
103- Suspicious File Creation in /etc for Persistence - 1c84dd64-7e6c-4bad-ac73-a5014ee37042
104
105### Response and remediation
106
107- Initiate the incident response process based on the outcome of the triage.
108- Isolate the involved host to prevent further post-compromise behavior.
109- If the triage identified malware, search the environment for additional compromised hosts.
110  - Implement temporary network rules, procedures, and segmentation to contain the malware.
111  - Stop suspicious processes.
112  - Immediately block the identified indicators of compromise (IoCs).
113  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
114- Remove and block malicious artifacts identified during triage.
115- 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.
116- Delete the maliciously created service/init.d files or restore it to the original configuration.
117- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
118- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
119- Leverage the incident response data and logging to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
120"""
121references = [
122    "https://www.intezer.com/blog/malware-analysis/hiddenwasp-malware-targeting-linux-systems/",
123    "https://pberba.github.io/security/2022/02/06/linux-threat-hunting-for-persistence-initialization-scripts-and-shell-configuration/#8-boot-or-logon-initialization-scripts-rc-scripts",
124    "https://www.cyberciti.biz/faq/how-to-enable-rc-local-shell-script-on-systemd-while-booting-linux-system/"
125
126]
127risk_score = 47
128rule_id = "474fd20e-14cc-49c5-8160-d9ab4ba16c8b"
129severity = "medium"
130tags = ["Domain: Endpoint", "OS: Linux", "Use Case: Threat Detection", "Tactic: Persistence", "Data Source: Elastic Endgame", "Resources: Investigation Guide", "Data Source: Elastic Defend"]
131timestamp_override = "event.ingested"
132type = "new_terms"
133query = '''
134host.os.type :"linux" and event.action:("creation" or "file_create_event" or "rename" or "file_rename_event") and 
135file.path : /etc/init.d/* and not process.name : ("dpkg" or "dockerd" or "rpm" or "dnf" or "chef-client" or "apk" or "yum" or 
136"rpm" or "vmis-launcher" or "exe") and not file.extension : ("swp" or "swx")
137'''
138
139[[rule.threat]]
140framework = "MITRE ATT&CK"
141
142[[rule.threat.technique]]
143id = "T1037"
144name = "Boot or Logon Initialization Scripts"
145reference = "https://attack.mitre.org/techniques/T1037/"
146
147[rule.threat.tactic]
148id = "TA0003"
149name = "Persistence"
150reference = "https://attack.mitre.org/tactics/TA0003/"
151
152[rule.new_terms]
153field = "new_terms_fields"
154value = ["file.path", "process.name"]
155
156[[rule.new_terms.history_window_start]]
157field = "history_window_start"
158value = "now-7d"