Linux Server Security · Automated

Linux server security
that works out of the box

The average Linux VPS receives its first attack within minutes of going online. Defensia detects and blocks them automatically — SSH brute force, web exploits, scanners, and more.

Install in 30 seconds →
LIVE ATTACK LOG — what's hitting your server right now

sshd: Failed password for root from 185.220.101.7 port 43992

sshd: Invalid user admin from 45.83.64.11 port 55120

nginx: 103.145.13.90 "GET /wp-login.php HTTP/1.1" 404

nginx: 91.108.4.30 "POST /../../../etc/passwd HTTP/1.1" 400

sshd: Failed password for ubuntu from 45.83.64.11 port 22180

… thousands more today

Why Linux servers get attacked

Linux powers 96% of the world's web servers. That makes it the #1 target for automated attacks. Botnets scan the entire IPv4 range in under 45 minutes, probing for open SSH ports, exposed databases, and unpatched web applications.

4.2K
attacks per server per day
Based on Defensia telemetry across 9 production servers
22 min
time to first attack after deploy
Median across new VPS deployments monitored by Defensia
250K+
attacks analyzed and blocked
Cumulative across all Defensia-protected servers

Most attacks are automated — bots don't care about your site size or traffic. They probe every server looking for easy wins: default credentials, unpatched software, and exposed admin panels. Without automated protection, you're relying on luck.

The biggest threats to Linux servers in 2026

Attack vectors evolve every year. These are the most common threats Defensia detects right now.

SSH brute force & credential stuffing

The #1 attack vector. Bots try thousands of username/password combinations per hour. Default credentials like root:admin are tested within minutes of a server going online.

How Defensia blocks SSH attacks →

Web application exploits (OWASP Top 10)

SQL injection, XSS, path traversal, remote code execution, and server-side request forgery. Automated scanners probe every web server for these vulnerabilities 24/7.

See WAF detection details →

Cryptominers & malware

Attackers install cryptocurrency miners that consume 100% CPU. Web shells in upload directories give persistent backdoor access. PHP malware hides in WordPress plugins and themes.

Rootkits & privilege escalation

Hidden processes, modified system binaries, and ld.so.preload hooks. Rootkits persist across reboots and are invisible to standard monitoring tools.

Exposed databases & services

MySQL, PostgreSQL, MongoDB, and Redis exposed to the internet with default credentials. Attackers dump data or use them as pivot points into your network.

Database protection details →

Unpatched CVEs

Known vulnerabilities in OpenSSH, nginx, Apache, PHP, and system libraries. Attackers scan for specific CVEs and exploit them within hours of public disclosure.

How to know if your server has been compromised

Most compromised servers show no obvious symptoms. Here's what to look for:

Warning signs of a compromised Linux server
Unexpected CPU spikes — cryptominers often consume 100% CPU on all cores, especially during off-hours
Unknown processes in /tmp or /dev/shm — malware typically hides executables in world-writable directories
Modified system binaries — rootkits replace ls, ps, netstat with versions that hide malicious processes
New SSH authorized_keys entries — attackers add their own public keys for persistent access
World-readable .env files — exposed database credentials, API keys, and secrets
Unexpected cron jobs — persistence mechanism that re-downloads malware after cleanup
Outbound connections to unknown IPs — C2 communication, data exfiltration, or spam relay activity
PHP files in upload directories — web shells disguised as images or placed in wp-content/uploads

Defensia's Security Score (0-100, A-F grade) continuously checks these indicators. The malware scanner detects cryptominers, reverse shells, and web shells in upload directories. See all detection capabilities →

Every attack type, detected automatically

Defensia monitors multiple attack surfaces simultaneously, with no configuration.

SSH Brute Force

15 detection patterns covering failed passwords, invalid users, pre-auth scanning, PAM failures, and kex negotiation drops.

Deep dive into SSH protection →

Web Application Attacks

SQL injection, XSS, path traversal, RCE, web shells, shellshock, SSRF, and 8 more OWASP attack types from nginx/Apache logs.

See all WAF detection rules →

Port & Network Scanning

Detects automated scanners (Shodan, Masscan, nmap) probing your services. Blacklists them before they find an open port.

Bot & Crawler Abuse

70+ bot fingerprints. Per-policy: allow legitimate bots (Googlebot), log gray-area crawlers, block malicious scanners.

Honeypot Trap Hits

Decoy endpoints that only attackers visit. Any request to /backup.zip, /.git, /phpmyadmin triggers immediate high-score ban.

WordPress Attacks

Dedicated detection for wp-login.php brute force, xmlrpc.php abuse, and plugin vulnerability probing.

Malware & Web Shells

File-level malware scanning with 64K+ hash signatures. Detects PHP backdoors, obfuscated shells, cryptominers, and suspicious executables in upload directories.

Email Server Attacks

11 detection patterns for Postfix SASL, Dovecot IMAP, and Roundcube login brute force. Auto-detected from mail.log.

Email server protection details →

How Defensia works

A lightweight Go agent runs on your server, reads logs in real time, and applies firewall rules automatically.

# Architecture

auth.log + nginx/access.log + docker logs

│ Auto-detected. No config files.

Watcher goroutines

│ Detect patterns in real time

Scoring engine → each attack adds points to IP score

│ Score ≥ 80 → block 1h · Score ≥ 100 → blacklist 24h

ipset add defensia-bans <IP> → firewall blocks instantly

│ 65,000+ concurrent bans with ipset

POST /api/agent/bans → dashboard + all your other servers

Linux server security checklist: what Defensia covers automatically

Most hardening guides list 20+ manual steps. Defensia handles the critical ones out of the box.

Security checkManualDefensia
Block SSH brute force attacksfail2ban + config
Detect web application exploits (WAF)ModSecurity + rules
Scan for malware & web shellsClamAV + cron
Monitor for CVE vulnerabilitiesManual apt audit
Block by country (geoblocking)iptables + GeoIP DB
Real-time attack dashboardNot available
Multi-server ban propagationNot available
Detect exposed database portsnmap + manual check
Security posture score (0-100)Lynis + manual review
Rootkit detectionrkhunter + chkrootkit
Slack / email / Discord alertsCustom scripts
Monitor Docker containersdocker logs + scripts

Everything included

Free tier covers the essentials. Pro adds deeper security intelligence.

FREE

SSH Protection

15 detection patterns. Blocks within seconds of attack start.

PRO

Web Firewall (WAF)

OWASP attack detection from nginx/Apache logs. Zero config.

FREE

Real-time Dashboard

Live event feed, charts, ban timeline, all servers in one view.

PRO

Malware Scanner

64K+ hash signatures. Web shells, cryptominers, rootkit checks.

PRO

CVE Intelligence

Detects vulnerable packages and matches against CISA KEV catalog.

PRO

Geoblocking

Block entire countries at the firewall level. Per-server policy.

PRO

Security Score

0-100 score (A-F grade). SSH, firewall, file permissions, credentials.

PRO

Bot Management

70+ bot fingerprints. Allow, log, or block per policy.

PRO

Alerts

Slack, email, Discord, and webhook notifications on attacks.

Supported Linux distributions

Ubuntu 20.04+
Debian 11+
CentOS 7+
RHEL 8+
Rocky Linux 8+
AlmaLinux 8+
Fedora 36+
Amazon Linux 2023

Requires: iptables + systemd + root access. Recommended: ipset.

Frequently asked questions

What is the best Linux server security tool?

It depends on your needs. For automated, zero-config protection that covers SSH, WAF, malware scanning, and CVE detection with a real-time dashboard, Defensia is purpose-built for that. For manual, granular control, tools like fail2ban (SSH only) or CrowdSec (requires YAML config) are alternatives. Defensia combines what would normally require 4-5 separate tools into one agent.

How do I protect my Linux server from brute force attacks?

Install a tool that monitors authentication logs (auth.log, secure) and automatically bans IPs after repeated failures. Defensia detects 15 SSH attack patterns including failed passwords, invalid users, pre-auth drops, and PAM failures. It blocks attackers within seconds using ipset, supporting 65,000+ concurrent bans. No configuration files needed.

Does Linux need a firewall?

Yes. Every Linux server exposed to the internet receives automated attacks within minutes. A firewall alone (iptables/nftables) blocks ports, but doesn't detect application-level attacks like SQL injection or credential stuffing. Defensia adds intelligent detection on top of firewall rules — it reads your logs, scores each IP, and blocks attackers dynamically.

How do I monitor my Linux server for attacks?

You can manually grep through auth.log and access.log, but that doesn't scale. Defensia provides a real-time web dashboard showing every attack, ban, and security event across all your servers. Live charts, event feed, ban timeline, and geographic distribution — all without touching a terminal.

How do I check if my Linux server has malware?

Defensia includes a malware scanner with 64,000+ hash signatures and 684 dynamic detection patterns. It checks for PHP web shells in upload directories, cryptominers, reverse shells, suspicious executables in /tmp, modified system binaries, and rootkit indicators like ld.so.preload hooks. Scans run on schedule and results appear in the dashboard.

What Linux distributions does Defensia support?

Ubuntu 20+, Debian 11+, CentOS 7+, RHEL 8+, Rocky Linux, AlmaLinux, Fedora 36+, and Amazon Linux 2023. The agent requires systemd, iptables, and root access. It also runs as a Docker container or Kubernetes DaemonSet via Helm.

Is Defensia open source?

The agent that runs on your server is MIT licensed and available on GitHub. It's written in Go and uses under 30MB of memory. The dashboard is a commercial SaaS with a free tier for one server.

How much does Linux server security cost?

Defensia is free for 1 server (includes SSH protection, dashboard, and basic features). Pro costs €9/server/month (or €7 billed annually) and includes WAF, malware scanning, CVE intelligence, geoblocking, bot management, and alerts. No cPanel or control panel license required.

Start protecting your server now

One command. Under 30 seconds. Free for one server.

$ curl -fsSL https://defensia.cloud/install.sh | sudo bash
Create Free Account

No credit card required.