Auth Failures
Spot brute-force and misconfig patterns in auth logs — defender view on $LAB.
Visual · t16_auth_failures
Auth failures = signal, not invitation to attack strangers. Original Cyberlium.
Ten failed logons might be a typo — ten thousand might be a scanner on YOUR lab honeypot you documented.
Correlate failed logon bursts: repeated usernames, rotating usernames, single source IP vs distributed, failure reason codes (Windows 4625 substatus; Linux 'Failed password' / 'Invalid user'). Learn baseline vs anomaly on YOUR lab by generating safe failed logins you control — never run password sprays against real accounts, classmates, or internet-facing hosts without authorization.
1. Windows failure signals
4625 clusters with same TargetUserName and WorkstationName or Source Network Address.
Substatus codes distinguish bad password vs locked vs unknown user — literacy for triage.
Command guide
Try these commands — Windows failure signals
═══ TOOLS & WEBSITES ═══ Browse / read these (authorized learning only — stay in YOUR lab / program scope)
Auth failure detection — https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html fail2ban — https://www.fail2ban.org/wiki/index.php/Main_Page
═══ INSTALL ═══
Linux (Debian/Ubuntu):
macOS:
Windows:
═══ LINUX / macOS ═══
Command — copy this
journalctl -n 100 --no-pager 2>/dev/null | grep -iE 'Failed password|Invalid user|authentication failure' | head -10 || grep -i failed /var/log/auth.log 2>/dev/null | tail -5 sudo fail2ban-client status 2>/dev/null || echo 'fail2ban not installed — optional on YOUR lab'
Primary tools to practice this lesson: journalctl, grep, fail2ban-client. Reference sites: Auth failure detection (https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html); fail2ban (https://www.fail2ban.org/wiki/index.php/Main_Page). Run every command in the box — install first, then the usage lines — only on YOUR lab / program scope.
2. Linux failure signals
sshd 'Failed password for invalid user' vs valid user — different threat stories.
PAM failures on sudo/su — watch for privilege attempts after auth noise.
3. Defender response literacy
Rate limit, block source, enforce lockout policy, alert SOC — on systems you administer.
No 'practice' credential guessing on production, classmates, or stranger SSH banners.
4. What you ship: auth failure pattern notes
Windows + Linux failure signals + safe lab generation method + NEVER spray strangers.
5. What you record before the next lesson
Auth failure pattern paragraph.
6. Wrong vs right: stranger hosts vs YOUR lab hosts
Worked failure — same MSF word, opposite target. Right never needs a café Wi-Fi or classmate laptop.
- Wrong: Run password spray against a classmate's SSH 'to see logs.'
- Right: Name failure patterns. Next: OS logs lab.
Mission: auth failure triage sheet
1) Generate one failed login on $LAB Windows and Linux (wrong password you control). 2) Capture log line or Event ID. 3) Write NEVER credential spray on stranger hosts.
Stuck? Ask Cyberlium AI Mentor
Ask Mentor: “4625 substatus 0xC000006D meaning?”
APPLY: Burst of 4625 events suggests:
APPLY: True or False: Password spraying strangers is defender lab.
APPLY: Safe lab auth failure: