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User Account Creation

Elastic Stack Serverless Security

Identifies attempts to create new users. This is sometimes done by attackers to increase access or establish persistence on a system or domain.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Persistence

Version: 13

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

Attackers may create new accounts (both local and domain) to maintain access to victim systems.

This rule identifies the usage of net.exe to create new accounts.

  • 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.
  • Identify the user account that performed the action and whether it should perform this kind of action.
  • Identify if the account was added to privileged groups or assigned special privileges after creation.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Account creation is a common administrative task, so there is a high chance of the activity being legitimate. Before
    investigating further, verify that this activity is not benign.
  • Creation of a Hidden Local User Account - 2edc8076-291e-41e9-81e4-e3fcbc97ae5e
  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved host to prevent further post-compromise behavior.
  • Delete the created account.
  • 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.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • 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).

Rule query

process where event.type in ("start", "process_started") and
  process.name : ("net.exe", "net1.exe") and
  not process.parent.name : "net.exe" and
  (process.args : "user" and process.args : ("/ad", "/add"))

Framework: MITRE ATT&CKTM