persistence_via_sysv_init.md

Persistence via System V Init

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Metadata

• Author: Elastic

• Description: This hunt identifies potential persistence mechanisms via System V Init on Linux systems. System V Init is a legacy init system used in many Linux distributions. System V Init uses scripts in /etc/init.d/ to start and stop services. These queries monitor for file creation/modification and process execution events in directories and files associated with System V Init services. These activities can indicate attempts to establish persistence through System V Init configurations. The hunt lists detailed information for further analysis and investigation.

• UUID: 27d76f07-7dc4-49bc-b4a7-6d9a01de171f

• Integration: endpoint

• Language: [ES|QL, SQL]

• Source File: Persistence via System V Init

Query

from logs-endpoint.events.file-*
| where @timestamp > NOW() - 30 day
| where host.os.type == "linux" and event.type in ("creation", "change") and file.path like "/etc/init.d/*" and
not process.name in ("dpkg", "dockerd", "yum", "dnf", "snapd", "pacman")
| eval persistence = case(file.path like "/etc/init.d/*", process.name, null)
| stats pers_count = count(persistence), agent_count = count_distinct(agent.id) by process.executable, file.path
| where pers_count > 0 and pers_count <= 20 and agent_count <= 3
| sort pers_count asc
| limit 100

from logs-endpoint.events.process-*
| where @timestamp > now() - 30 day
| where host.os.type == "linux" and event.type == "start" and event.action == "exec" and process.parent.executable like "/etc/init.d/*"
| stats cc = count(), host_count = count_distinct(host.name) by process.executable, process.parent.executable
| where cc > 0 and cc <= 20 and host_count <= 3
| sort cc asc
| limit 100

SELECT name, path, source, status, type FROM startup_items
WHERE type == "systemd unit" AND status == "active" AND
source LIKE "/etc/init.d/%"

SELECT 
    f.filename, 
    f.path, 
    u.username AS file_owner, 
    g.groupname AS group_owner, 
    datetime(f.atime, 'unixepoch') AS file_last_access_time, 
    datetime(f.mtime, 'unixepoch') AS file_last_modified_time, 
    datetime(f.ctime, 'unixepoch') AS file_last_status_change_time, 
    datetime(f.btime, 'unixepoch') AS file_created_time, 
    f.size AS size_bytes,
    h.md5 
FROM 
    file f 
LEFT JOIN 
    users u ON f.uid = u.uid 
LEFT JOIN 
    groups g ON f.gid = g.gid 
LEFT JOIN 
    hash h ON f.path = h.path 
WHERE 
    f.directory IN ('/etc/init.d/')
ORDER BY 
    f.mtime DESC;

Notes

• This hunt includes multiple ES|QL and OSQuery queries to identify potential persistence mechanisms via System V Init on Linux systems.
• Detects file creation or modification events in directories and files associated with System V Init services, such as /etc/init.d/.
• Detects processes started by System V Init scripts in /etc/init.d/.
• Uses OSQuery to detect active System V Init services and retrieve detailed file information related to System V Init services.
• Uses OSQuery to retrieve file information for files in /etc/init.d/.
• Excludes common legitimate processes and file types to minimize false positives.

MITRE ATT&CK Techniques

• T1037

License

• Elastic License v2