Common Linux Security Mistakes

Over decades, the Unix and Linux communities have learned hard lessons from common security misconfigurations and bad practices. Below is a timeline of the most significant "security sins" — what went wrong, the risks involved, and how modern best practices fixed them.

#	Year (approx.)	Sin / Bad Practice	Problem / Risk	How It Got Fixed
1	1970s–1980s	Running everything as root	Any bug or mistake could compromise entire system	Introduced user separation, sudo, and principle of least privilege
2	1980s–1990s	Using Telnet, rlogin, rsh for remote access	Transmitted passwords in plaintext; network sniffing risk	Replaced with SSH (encrypted remote access)
3	1980s–1990s	Trusting hosts via .rhosts files	Compromise of one trusted host allowed login to others	Switched to user-based authentication, SSH keys, and disabled .rhosts
4	1970s–1990s	Storing passwords in /etc/passwd (or plaintext)	Any user could read password hashes or cleartext passwords	Moved to /etc/shadow with proper permissions and strong hashing
5	1980s–2000s	Default open network services (FTP, NFS, SMTP, SNMP, etc.)	Increased attack surface; remote exploitation possible	Adopted firewalls, disabled unnecessary services, hardened configs
6	1990s	Weak password policies	Easy-to-guess passwords allowed full account compromise	Introduced password complexity requirements, PAM modules, and account lockouts
7	1990s–2000s	World-writable /tmp and / directories	Local users could overwrite important files or escalate privileges	Enforced sticky bits, permissions hygiene, and separate mount options
8	1990s–2000s	SUID/SGID binaries mismanagement	Could be abused for root escalation	Audited and minimized SUID/SGID binaries; applied secure alternatives
9	2000s	Unpatched kernel and core utilities	Any vulnerability could be exploited locally or remotely	Shift to regular patching, package managers, and security advisories
10	2000s	Poor logging and auditing	Intrusions went unnoticed	Implemented syslog, auditd, and monitoring tools for accountability

These lessons from the past have shaped today’s secure Linux practices. Don’t repeat history — avoid these mistakes by contacting us for professional system hardening, security audits, and ongoing support.

We bring decades of Unix/Linux experience to ensure your systems follow modern best practices from day one.