security-audit

Security Audit

Audit Linux system security configurations and recommend hardening measures.

Instructions

1. Check each security category below
2. Document findings with severity
3. Provide specific remediation steps
4. Prioritize critical issues

SSH configuration

# Check SSH config
grep -E "^(PermitRootLogin|PasswordAuthentication|PubkeyAuthentication|Port)" /etc/ssh/sshd_config

# Recommended settings
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes

Critical: Flag if PermitRootLogin yes or PasswordAuthentication yes

Firewall

# UFW status
ufw status verbose

# iptables
iptables -L -n -v
ip6tables -L -n -v

# nftables
nft list ruleset

Critical: Flag if firewall is disabled or allows 0.0.0.0/0 on sensitive ports

User accounts

# Users with login shells
grep -v '/nologin\|/false' /etc/passwd

# Users with empty passwords
awk -F: '($2 == "") {print $1}' /etc/shadow

# Sudoers
grep -v '^#' /etc/sudoers /etc/sudoers.d/* 2>/dev/null

# Check for unauthorized sudo
grep NOPASSWD /etc/sudoers /etc/sudoers.d/*

File permissions

# World-writable files
find / -type f -perm -002 2>/dev/null

# SUID/SGID binaries
find / -type f \( -perm -4000 -o -perm -2000 \) 2>/dev/null

# SSH key permissions
ls -la ~/.ssh/

Services and ports

# Listening services
ss -tuln

# Enabled services
systemctl list-unit-files --state=enabled

# Running services
systemctl list-units --type=service --state=running

Updates

# Pending security updates
apt list --upgradable 2>/dev/null | grep -i security
dnf check-update --security 2>/dev/null

# Kernel version
uname -r

Output format

## Critical Issues
- [ ] SSH allows root login with password

## Warnings
- [ ] Firewall allows port 22 from any IP

## Recommendations
- [ ] Enable automatic security updates
- [ ] Configure fail2ban

## Passed Checks
- [x] No users with empty passwords

Rules

• MUST check all categories before concluding
• MUST prioritize by severity (critical > warning > info)
• MUST provide specific remediation commands
• Never disable security features without explicit approval
• Never expose found credentials or sensitive data
• Always recommend backup before making changes