Even though we know that Linux is quite secure by default installation of nearly any distribution, if you want to be sure that it is secure enough there are applications and services available that will make your computer/system more secure and manageable.

Antivirus

• Clam AntiVirus – Extremely popular antivirus solution for UNIX based machines. Includes real time virus scanning and a virus definition database updated multiple times per day.
• AVScan – A front-end for Clam AntiVirus.
• AVG Anti-Virus – Effective virus scanning suite. Requires regular virus definition updates.
• Avast Home Edition  – Complete antivirus suite including real time scanning, email protection, internet traffic filtering, a firewall and more.

RootkitRootkits are about the nastiest forms of malware around. To keep your computer (and your privacy) safe, you’ll need an application to scan for rootkits.

• chkrootkit  – The definitive solution for finding and removing rootkits from Linux machines.

Firewall

• Firestarter – Real time firewall that monitors all of the open ports and active network connections on your computer. Allows you to specify a very strict rule set.
• Firewall Builder  – Useful tool for assembling a firewall rule set or policy for popular UNIX based firewalls including iptables, ipfilter, etc.
• TuxGuardian  – Verifies the integrity of applications trying to gain access to the network. Useful for preventing viruses, trojans, spyware, etc. from spreading throughout the network.
• HardWall Firewall  – Iptables based script that performs detailed packet inspection and filtering to keep your computer free from malicious traffic.
• BullDog  – Complex firewall for advanced users.

Email

• Smart sendmail filters  – A collection of tools to block and filter sendmail spam as well as scan attachments for viruses.
• Sagator – An interface for the postfix, sendmail and other smtpd gateways that run popular antivirus and antispam solutions.

Web Utility

1. Tor  – Uses a network of virtual tunnels to
   provide anonymity for surfing the internet and transferring files over a network.
2. WebCleaner  – Allows you to control the type of data your proxy parses. Useful for eliminating dangerous malware and removing annoying popup ads.

Network

1. SmoothWall  – Firewall, IDS and VPN system for home users and networks.
2. Nagios  – Comprehensive web based tool equipped with virtually every imaginable feature for knowing exactly what’s going on in your network.
3. nLive Core  – Monitors the traffic that traverses your network via packet inspection and filtering.
4. Nessus  – Industry leading open source network vulnerability scanner. Highly scalable and very thorough.

Intrusion Detection System

• Snort  – The premier free IDS solution. Detects a wide variety of attacks including buffer overflows, OS fingerprinting, CGI scans and more. Uses real time traffic analysis and packet logging on IP networks.
• HenWen [Mac] – Effective implementation of Snort IDS for Mac users.
• Open Source Host-based Intrusion Detection System  – Personal IDS performing log analysis, registry monitoring, malware detection, time-based alerting and active response.
• Prelude  – Detects system anomalies and reports findings to the user. Also analyzes logs for anomalies.

Virtual Private Network

• SSL-Explorer  – Highly scalable VPN that integrates directly into your browser. Requires only a single open port to work.
• OpenVPN – Popular VPN solution specializing in remote access.
• strongSwan – IPsec based VPN using multiple encryption methods.

Wireless

• Kismet  – Very popular wireless network detector, sniffer, and IDS.

Encryption

1. GNU Privacy Guard  – A command line based encryption tool using multiple encryption algorithms including OpenPGP, AES, SHA-1, and more.
2. TrueCrypt  – Creates virtual encrypted drives.

The list is of course not complete and there are a lot more applications that you can find for securing your Linux box. Also check out the security section on this blog to find some more on this.