linux-hardening
Apply CIS benchmarks and secure Linux servers. Configure SSH, manage users, implement firewall rules, and enable security features. Use when hardening Linux systems for production or meeting security compliance requirements.
How do I install this agent skill?
npx skills add https://github.com/bagelhole/devops-security-agent-skills --skill linux-hardeningIs this agent skill safe to install?
- Gen Agent Trust Hubpass
The skill provides a comprehensive set of scripts and configuration templates for Linux system hardening and security auditing based on CIS benchmarks. It performs standard administrative tasks such as configuring SSH, firewall rules, and kernel parameters, all of which are consistent with its stated purpose.
- Socketpass
No alerts
- Snykwarn
Risk: MEDIUM · 1 issue
- Runlayerwarn
6/6 files flagged
- ZeroLeakspass
Score: 93/100 · 2 sections analyzed
What does this agent skill do?
Linux Hardening
Secure Linux servers following CIS benchmarks and security best practices.
When to Use This Skill
Use this skill when:
- Hardening production servers
- Meeting compliance requirements
- Implementing security baselines
- Configuring secure SSH access
SSH Hardening
# /etc/ssh/sshd_config
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
MaxAuthTries 3
ClientAliveInterval 300
ClientAliveCountMax 2
AllowUsers deploy admin
Protocol 2
User Security
# Password policy
sudo apt install libpam-pwquality
# /etc/security/pwquality.conf
minlen = 14
dcredit = -1
ucredit = -1
ocredit = -1
lcredit = -1
# Lock inactive accounts
useradd -D -f 30
# Audit sudo usage
echo "Defaults logfile=/var/log/sudo.log" >> /etc/sudoers
Firewall Configuration
# UFW setup
ufw default deny incoming
ufw default allow outgoing
ufw allow ssh
ufw allow 443/tcp
ufw enable
# Or iptables
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
Kernel Hardening
# /etc/sysctl.d/99-security.conf
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
kernel.randomize_va_space = 2
fs.suid_dumpable = 0
# Apply
sysctl -p
File Permissions
# Critical files
chmod 600 /etc/shadow
chmod 644 /etc/passwd
chmod 700 /root
chmod 600 /etc/ssh/sshd_config
# Find world-writable files
find / -type f -perm -0002 -ls
# Find SUID files
find / -perm -4000 -type f -ls
Audit Configuration
# Install auditd
apt install auditd
# /etc/audit/rules.d/audit.rules
-w /etc/passwd -p wa -k identity
-w /etc/shadow -p wa -k identity
-w /etc/sudoers -p wa -k actions
-a always,exit -F arch=b64 -S execve -k exec
Best Practices
- Disable unused services
- Keep system updated
- Use fail2ban for intrusion prevention
- Enable SELinux/AppArmor
- Regular security audits
- Monitor log files
- Implement least privilege
Related Skills
- cis-benchmarks - Compliance scanning
- firewall-config - Firewall rules
How can the creator link this skill?
Add the canonical catalog link to the repository README so users can inspect current installs and available audits. The publishing guide covers the complete discovery path.
<a href="https://skillzs.dev/skills/bagelhole/devops-security-agent-skills/linux-hardening">View linux-hardening on skillZs</a>