Suspicious Passwd File Event Action

Monitors for the generation of a passwd password entry via openssl, followed by a file write activity on the "/etc/passwd" file. The "/etc/passwd" file in Linux stores user account information, including usernames, user IDs, group IDs, home directories, and default shell paths. Attackers may exploit a misconfiguration in the "/etc/passwd" file permissions or other privileges to add a new entry to the "/etc/passwd" file with root permissions, and leverage this new user account to login as root.

Rule type: eql

Rule indices:

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

Version: 1

Rule authors:

Rule license: Elastic License v2

sequence by host.id, process.parent.pid with maxspan=1m
  [process where host.os.type == "linux" and event.type == "start" and event.action == "exec" and
   process.name == "openssl" and process.args == "passwd" and user.id != "0"]
  [file where event.dataset == "auditd_manager.auditd" and host.os.type == "linux" and file.path == "/etc/passwd" and
  process.parent.pid != 1 and not auditd.data.a2 == "80000" and event.outcome == "success" and user.id != "0"]