persistence_via_message_of_the_day.md

Persistence via Message-of-the-Day

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Metadata

• Author: Elastic

• Description: This hunt identifies potential persistence mechanisms via the message-of-the-day (motd) on Linux systems. It monitors for file creation or modification events in the /etc/update-motd.d directory and processes started by these motd scripts. These scripts launch on SSH/terminal connection events, and execute the scripts as root. These activities can indicate attempts to establish persistence through motd modifications.

• UUID: 5984a354-d76c-43e6-bdd9-228456f1b371

• Integration: endpoint

• Language: [ES|QL, SQL]

• Source File: Persistence via Message-of-the-Day

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/update-motd.d/*" and
not process.name in ("dpkg", "dockerd", "yum", "dnf", "snapd", "pacman")
| eval persistence = case(file.path like "/etc/update-motd.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 <= 5
| sort pers_count asc
| limit 100

from logs-endpoint.events.process-*
| where @timestamp > now() - 30 day
| where host.os.type == "linux" and event.action == "exec" and event.type == "start" and process.parent.executable like "/etc/update-motd.d/*" and
not process.args like "/tmp/tmp.*"
| stats cc = count(), host_count = count_distinct(host.name) by process.executable, process.parent.executable
| where host_count <= 5
| sort cc asc
| limit 100

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/update-motd.d/')
ORDER BY
    f.mtime DESC;

Notes

• This hunt includes multiple ES|QL and OSQuery queries to identify potential persistence mechanisms via the message-of-the-day (motd) on Linux systems.
• Detects file creation or modification events in the /etc/update-motd.d directory, which is used for message-of-the-day scripts.
• Excludes common legitimate processes to minimize false positives.
• Uses EVAL to tag potential persistence events and counts occurrences to identify unusual activity.
• Monitors processes started by motd scripts to detect potential persistence mechanisms.
• OSQuery query is provided to complement the detection by retrieving detailed file information related to motd scripts.

MITRE ATT&CK Techniques

• T1036.005
• T1546.003

License

• Elastic License v2