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The 5 Most Overlooked Linux Files That Could Expose Your Server to Hackers

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Intro:

You installed firewalls, disabled root login, and even configured fail2ban. You’re secure, right? Maybe not. In my security audits, the biggest threats didn’t come from open ports — they came from quietly ignored files that leak sensitive data or allow privilege escalation. Let’s go through 5 Linux files that most admins forget to check — and how to lock them down.

1. /var/log/auth.log (Ubuntu) or /var/log/secure (Red Hat)

Why it’s risky:

  • Reveals all login attempts — successful and failed
  • Can show usernames, IPs, and brute-force clues

What to do:

  • Monitor it regularly
  • Secure it with strict permissions:
  • sudo chmod 600 /var/log/auth.log

2. /etc/bash_history

Why it’s risky:

  • Often stores passwords, tokens, or sensitive commands

Best practices:

unset HISTFILEexport HISTSIZE=0

Or make it write-protected:

chmod 400…

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