Detect Default Accounts in Google Chronicle
Adversaries may obtain and abuse credentials of a default account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Default accounts are those built into an OS (e.g., Guest or Administrator on Windows, root on Linux), preset on network devices/appliances, or created automatically by software integrations (e.g., vpxuser on ESXi when joined to vCenter). Adversaries exploit organizations that fail to disable, rename, or change the passwords of these accounts post-installation.
MITRE ATT&CK
- Technique
- T1078 Valid Accounts
- Sub-technique
- T1078.001 Default Accounts
- Canonical reference
- https://attack.mitre.org/techniques/T1078/001/
YARA-L Detection Query
rule t1078_001_default_account_logon {
meta:
author = "Argus Detection Engineering"
description = "Detects authentication using default built-in system accounts (T1078.001)"
mitre_technique = "T1078.001"
mitre_tactic = "Initial Access, Persistence, Privilege Escalation, Defense Evasion"
severity = "HIGH"
priority = "HIGH"
events:
(
$auth.metadata.event_type = "USER_LOGIN" or
$auth.metadata.event_type = "USER_LOGIN_FAIL"
)
re.regex($auth.target.user.userid, `(?i)^(administrator|guest|defaultaccount|defaultuser|admin|root|vpxuser|dcadmin|sysadmin|service|support|user|test|demo|operator|sa|netadmin)$`)
$host = $auth.principal.hostname
match:
$host over 24h
outcome:
$risk_score = 75
$username = array_distinct($auth.target.user.userid)
$source_ip = array_distinct($auth.principal.ip)
$event_types = array_distinct($auth.metadata.event_type)
condition:
$auth
}
rule t1078_001_default_account_activation {
meta:
author = "Argus Detection Engineering"
description = "Detects command-line activation or privilege escalation of default built-in accounts (T1078.001)"
mitre_technique = "T1078.001"
severity = "CRITICAL"
priority = "HIGH"
events:
$proc.metadata.event_type = "PROCESS_LAUNCH"
re.regex($proc.target.process.command_line, `(?i)(net\s+user\s+(defaultaccount|guest|administrator)\s+/active:yes|net\s+localgroup\s+administrators\s+(guest|defaultaccount|administrator))`)
$host = $proc.principal.hostname
match:
$host over 24h
outcome:
$risk_score = 95
$cmdline = array_distinct($proc.target.process.command_line)
$actor = array_distinct($proc.principal.user.userid)
condition:
$proc
}Two Chronicle YARA-L 2.0 rules targeting T1078.001. The first matches USER_LOGIN and USER_LOGIN_FAIL UDM events where target.user.userid matches known default account names via case-insensitive anchored regex; it groups by hostname over 24 hours and outputs risk score, deduplicated usernames, source IPs, and event types. The second matches PROCESS_LAUNCH events where target.process.command_line contains net user or net localgroup commands activating default accounts, assigned a higher risk score of 95 as this represents direct account manipulation.
Data Sources
Required Tables
False Positives & Tuning
- Authorized system administrators using break-glass Administrator credentials during emergency access scenarios documented in ITSM change management systems.
- Automated provisioning pipelines using service or admin accounts to configure newly joined systems before domain integration and hardening is completed.
- Penetration testing engagements using default credentials as part of scope-approved internal red-team assessments against managed endpoints — correlate against authorized test windows.
Other platforms for T1078.001
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Enable and Use Built-in DefaultAccount via PowerShell (Magic Hound TTP)
Expected signal: Sysmon Event ID 1: Process Create with CommandLine containing 'net user DefaultAccount /active:yes'. Windows Security Event ID 4722 (User Account Enabled) with TargetUserName=DefaultAccount. Windows Security Event ID 4725 (User Account Disabled) after cleanup. Security Event ID 4688 (process creation) if command-line auditing is enabled.
- Test 2Enable Built-in Guest Account and Verify Access
Expected signal: Windows Security Event ID 4722 (User Account Enabled) with TargetUserName=Guest. Windows Security Event ID 4688 or Sysmon Event ID 1 with CommandLine 'net user Guest /active:yes'. Security Event ID 4625 if subsequent logon attempt is made. Event ID 4725 on cleanup.
- Test 3Authenticate Using Built-in Administrator Account via Net Use (HyperStack-style IPC$ Access)
Expected signal: Windows Security Event ID 4648 (Logon using explicit credentials) with TargetUserName=Administrator and TargetServerName=127.0.0.1. Windows Security Event ID 4624 (logon type 3 - Network) or 4625 (failed logon) on the target host. Sysmon Event ID 1 with CommandLine 'net use \\127.0.0.1\IPC$'. Sysmon Event ID 3 (network connection) to port 445.
- Test 4Simulate Default Service Account Logon via Scheduled Task
Expected signal: Windows Security Event ID 4698 (Scheduled Task Created) with task name 'DefaultAccountTest'. Windows Security Event ID 4624 (SYSTEM logon type 5) when task executes. Sysmon Event ID 1 for schtasks.exe and cmd.exe processes. Sysmon Event ID 11 (File Created) for the output file in TEMP. Security Event ID 4699 (Scheduled Task Deleted) on cleanup.
References (14)
- https://attack.mitre.org/techniques/T1078/001/
- https://docs.microsoft.com/en-us/windows/security/identity-protection/access-control/local-accounts
- https://docs.aws.amazon.com/IAM/latest/UserGuide/id_root-user.html
- https://cloud.google.com/blog/topics/threat-intelligence/vmware-esxi-zero-day-bypass/
- https://pentera.io/blog/information-disclosure-in-vmware-vcenter/
- https://www.microsoft.com/security/blog/2020/04/02/attack-matrix-kubernetes/
- https://github.com/rapid7/metasploit-framework/tree/master/modules/exploits/linux/ssh
- https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-249a
- https://www.sygnia.co/blog/elephant-beetle-an-organized-financial-threat/
- https://thedfirreport.com/2021/11/15/exchange-exploit-leads-to-domain-wide-ransomware/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1078.001/T1078.001.md
- https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4624
- https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4625
- https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4722
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