103 Free Security Apps. for Windows, MAC, and Linux

Posted on March 10, 2010


How many times have you downloaded an app that could supposedly solve all of your computer problems absolutely free of cost? Now ask yourself how many times that app actually did what it was supposed to, or better yet how many times that app was actually free? More often than not your answer is going to be zero.

Unfortunately for all of us, most software providers use gimmicks to sucker consumers in to purchasing their enterprise security apps: Sure, they’ll keep your computer virus free for 30 days, but after that you’ll need a subscription. Otherwise they’ll just scan your registry for bugs but won’t fix them for you. Frankly, we’re tired of that.

To keep your computer safe (and save some cash while doing it) we’ve assembled a list of 103 free security apps for Mac, Windows and Linux. By the end of the article you should have enough resources to secure even the most naïve system, for free!


The biggest enemy of the internet user today is spyware. How many computers have you seen rendered useless because of 20 IE toolbars and 15 apps running in the background? To keep your computer running at full performance you need a spyware scanner.

  1. Ad-Aware SE Personal [Windows] – Popular, comprehensive spyware removal tool. Maintains a large blacklisted spyware database and identifies malicious program code for the best possible detection.
  2. Spyware Terminator [Windows] – Monitors all running processes in real time and determines their integrity. If spyware is found, moves the files to a quarantined section of the hard drive or deletes the files on system start-up.
  3. Spybot – Search & Destory [Windows] – Uses deep scanning techniques to cleanse your system of the most obscure forms of spyware. Allows you to blacklist certain types of spyware in order to prevent it from showing up on your system again.
  4. Winpooch [Windows] – Intercepts programs in real time via API hooking; determines the integrity of the program and shuts out spyware and Trojan horses from writing in a system directory, connecting to the internet, or doing anything harmful to the computer.
  5. SpywareBlaster [Windows] – Prevents the installation of ActiveX based spyware, blocks tracking cookies and restricts the actions of malicious websites.
  6. Bazooka Adware and Spyware Scanner [Windows] – Scans your computer for the more popular types of spyware usually found bundled with software packages and removes the malicious content.
  7. Windows Defender [Windows] – Microsoft’s solution for protecting your computer from spyware and popups.
  8. MalWhere [Windows] – Displays detailed information about the processes running on your computer including those that run at start up. Investigates suspicious processes and let’s you know when malicious code is being executed. Does not require a spyware definition updating.
  9. Trend Micro Anti-Spyware for the Web [Web: Windows] – Online based spyware detection and removal tookit. Perfect solution for non tech savvy users.
  10. Zebra scanner [Mac] – Scans files for hidden agendas (e.g. a trojan disguised as an MP3 or image.) Notifies the user of the scanned files integrity. Does not contain a method for disinfecting the computer.


Perhaps the ultimate definition of computer security is the effectiveness of your antivirus. Antivirus software keeps the most problematic forms of malware from corrupting your computer.

  1. McAfee AVERT Stinger [Windows] – Tool used to remove specific current popular viruses and worms. Make sure to download the version of Stinger pertaining to the virus found on your machine.
  2. PC Tools AntiVirus [Windows] – Comprehensive virus scanning suite offering protection from malicious internet software, email attachments and boot sector viruses. Includes real time virus scanning.
  3. Clam AntiVirus [Linux] – Extremely popular antivirus solution for UNIX based machines. Includes real time virus scanning and a virus definition database updated multiple times per day.
  4. AVScan [Linux] – A front-end for Clam AntiVirus.
  5. ClamXav [Mac] – Uses ClamAV engine to scan files for viruses.
  6. AVG Anti-Virus [Windows, Linux] – Effective virus scanning suite. Requires regular virus definition updates.
  1. Avast Home Edition [Windows, Linux] – Complete antivirus suite including real time scanning, email protection, internet traffic filtering, a firewall and more.
  2. Housecall [Web: Windows, Linux, Mac] – Web based scanner that detects and removes viruses, worms, trojans and spyware. Also points out system vulnerabilities and offers advice on obtaining security patches.
  3. Symantec Security Check [Web] – Simple antivirus solution that searches your computer for various forms of malware and deletes them. Offers a secondary scan to measure the vulnerability of your computer.


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

  1. Sophos Anti-Rootkit [Windows] – Removes complex rootkits and various types of malware running in a hidden state from personal and network computers.
  2. Rootkit Hunter [Mac] – Searches for popular UNIX and Mac rootkits and removes them.
  3. chkrootkit [Linux] – The definitive solution for finding and removing rootkits from Linux machines.


A well regarded firewall with a strict rule set is the first line of defense against intruders. Keep hackers from sneaking malware onto your system in the first place with these freebie firewall solutions.

  1. ZoneAlarm [Windows] – Popular, comprehensive firewall suite including a highly customizable rule set and a very effective warning system letting you know when your computer is at risk. Be sure to select “I only want basic ZoneAlarm protection” from the download screen (otherwise you’ll end up with a trial version.)
  2. VisualZone [Windows] – Analyzes ZoneAlarm information including intrusion types and methods of entry. Allows you to gain a clear view of your system’s vulnerabilities.
  3. PC Tools Firewall Plus [Windows] – User friendly firewall that monitors the applications connecting to the network. Uses a simple rule set to prevent malware from infecting your computer.
  4. Firestarter [Linux] – 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.
  5. Firewall Builder [Linux] – Useful tool for assembling a firewall rule set or policy for popular UNIX based firewalls including iptables, ipfilter, etc.
  6. TuxGuardian [Linux] – Verifies the integrity of applications trying to gain access to the network. Useful for preventing viruses, trojans, spyware, etc. from spreading throughout the network.
  7. HardWall Firewall [Linux] – Iptables based script that performs detailed packet inspection and filtering to keep your computer free from malicious traffic.
  8. BullDog [Linux] – Complex firewall for advanced users.
  9. PeerGuardian [Windows, Linux, Mac] – Blocks IPs from accessing your network. Especially useful for protecting your privacy when using peer to peer software.


Despite being one of the most commonly used features on our computers, email ranks among the most insecure. Email attachments are the primary gateway for inviting viruses onto your computer. Here are a few apps to cleanup your inbox and keep your computer secure.

  1. Thunderbird [Windows, Linux, Mac] – Highly customizable secure email client. Comes equipped with spam email filters, phishing protection and encryption capabilities.
  2. Smart sendmail filters [Linux] – A collection of tools to block and filter sendmail spam as well as scan attachments for viruses.
  3. Sagator [Linux] – An interface for the postfix, sendmail and other smtpd gateways that run popular antivirus and antispam solutions.
  4. Tiger Envelopes [Windows, Linux, Mac] – Encrypts email messages. Integrates into Outlook, Thunderbird, Mac Mail and KMail.
  5. Simple ASCII Email Encoder [Mac] – Encodes your email address with ASCII values to prevent unsolicited spam mail from winding up in your inbox.

Web Utility

Malware infestation is probably the most annoying aspect of surfing the internet. It starts by accidentally downloading a toolbar here, failing to read a EULA there, and eventually your whole computer is one big slow piece of junk. To prevent this from happening (again) try using these apps when surfing.

  1. WinSCP [Windows] – SFTP and SCP client for transferring files to remote hosts. Includes text editor for editing remote documents.
  2. Privacy Mantra [Windows] – Erases data stored in your internet history, cookies, cache, index.dat, auto complete forms and more to protect your privacy.
  3. Tor [Windows, Linux, Mac] – Uses a network of virtual tunnels to provide anonymity for surfing the internet and transferring files over a network.
  4. BarracudaDrive [Windows, Linux, Mac] – Free secure web server implementation. Useful for managing files remotely.
  5. Firefox [Windows, Linux, Mac] – A fan favorite browser for it’s secure architecture and available add-ons. Uses SSL browsing by default.
  6. McAfee Site Advisor [Windows, Linux, Mac] – Rates websites by their ability to infect your computer with malware. Advises you if a site is safe or not.
  7. Opera [Windows, Linux, Mac] – Secure multi-platform web browser.
  8. PuTTY [Windows, Linux] – Telent and SSH client for running remote sessions. Main features include command line based SCP and SFTP clients. Frequently used to communicate between a Windows machine and a Unix machine.
  9. WebCleaner [Linux] – Allows you to control the type of data your proxy parses. Useful for eliminating dangerous malware and removing annoying popup ads.
  10. Cyberduck [Mac] – Uses SSH to transfer files to remote computers and networks. Also integrates into OS X features including Bonjour, Keychain, iDisk and more.


With an insecure network not only will you be vulnerable to the perils of the internet, everyone connected to your network will too. Meaning instead of having one computer down due to a nasty virus, you could have hundreds. These freebie apps will help you manage the challenge of keeping your network safe.

  1. SoftPerfect Network Scanner [Windows] – Displays information about the configuration of your network.
  2. SecureRDP [Windows] – Allows you to monitor and reject the incoming RDP connections to your server.
  3. Colasoft Packet Player [Windows] – Capture packets and trace their route through your network. Extremely useful for finding bottlenecks and vulnerable points.
  4. DomainScan Light [Windows] – Monitor open ports, connected devices, changes made to your network.
  5. SmoothWall [Linux] – Firewall, IDS and VPN system for home users and networks.
  6. Nagios [Linux] – Comprehensive web based tool equipped with virtually every imaginable feature for knowing exactly what’s going on in your network.
  7. nLive Core [Linux] – Monitors the traffic that traverses your network via packet inspection and filtering.
  8. Network Mapper [Windows, Linux, Mac] – Uses packets passing through the network to find out what hosts are available, what services they’re offering, what operating system they’re running and what type of packet filtration/firewall they’re using.
  9. Wireshark [Windows, Linux, Mac] – Powerful tool for capturing network protocol data for analysis. Contains more than 25 methods for reading packets making it useful for a wide array of networks.
  10. Nessus [Windows, Linux, Mac] – Industry leading open source network vulnerability scanner. Highly scalable and very thorough.
  11. dSniff Control [Mac] – Tool used to test the security of your network. Tries various sniffing and spoofing exploits to gain information about your network.
  12. Flame [Mac] – Simple tool used to breakdown the status and events taking place in your network.
  13. Server Admin Tools [Mac] – Apple’s solution for securing and monitoring a network.

Intrusion Detection System

Implementing an effective intrusion detection system is a surefire step to improving the security of your network and personal computer. Here are several popular solutions.

  1. Snort [Windows, Linux, Mac] – 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.
  2. HenWen [Mac] – Effective implementation of Snort IDS for Mac users.
  3. Open Source Host-based Intrusion Detection System [Windows, Linux, Mac] – Personal IDS performing log analysis, registry monitoring, malware detection, time-based alerting and active response.
  4. Prelude [Linux] – Detects system anomalies and reports findings to the user. Also analyzes logs for anomalies.

Virtual Private Network

VPN usage has exploded the past few years due to its new found ease of use and high level of security.

  1. SSL-Explorer [Windows, Linux, Mac] – Highly scalable VPN that integrates directly into your browser. Requires only a single open port to work.
  2. OpenVPN [Windows, Linux, Mac] – Popular VPN solution specializing in remote access.
  3. IPSecuritas [Mac] – IPsec based VPN allowing you to transfer secure data remotely.
  4. strongSwan [Linux] – IPsec based VPN using multiple encryption methods.

Temporary Files

What websites have you been visiting? What’s that, too embarrassed to say? Don’t worry, we’ve got you covered. Simply use one of these apps to delete all of your temporary files and clean up the trail you left behind.

  1. HijackThis [Windows] – Scans your computers browser, registry and operating system settings to generate a report of the state of your computer. Allows you to select which software and settings to delete.
  2. Zappit System Cleaner [Windows] – Cleans up the footprints you leave when using the computer including: temporary files, recent documents, search and run commands, auto complete internet forms and history and more.
  3. CCleaner [Windows] – A system optimization and privacy tool that cleans up the registry, temporary files, cookies, web history and cache and more.
  4. WinXPatch [Windows] – A tool used to perform several security upgrades to the default installation and registry.
  5. Advanced WindowsCare v2 Personal [Windows] – Cleans up temporary files and the registry to maximize your privacy. Also doubles as a spyware remover.
  6. EasyCleaner [Windows] – A comprehensive tool for cleaning up the registry and deleting your footprints on the computer. Includes software to manage programs at start up and free up disk space.
  7. CleanCache [Windows] – Deletes the temporary files you leave behind when you surf the internet.
  8. xpy [Windows] – Improves the general security of your system by reconfiguring some of the default computer settings.
  9. Cookie Eraser [Windows] – A tool to help you identify and erase the unnecessary cookies on your computer.
  10. Yet Another System Utility [Mac] – Clears the cache, browser history and other areas where you might have left a footprint while using the computer.


Securing your WiFi network is easier than it sounds. By taking a few extra minutes to install a few of the following apps, you’ll have your WiFi network on lockdown in no time.

  1. Kismet [Linux, Mac] – Very popular wireless network detector, sniffer, and IDS.
  2. AirSnare [Windows] – Wireless IDS that alerts you when an unfriendly MAC address is trying to access your network.
  3. myWIFIzone [Windows] – Acts as a gateway to block people from accessing your WiFi connection without receiving permission from you first.
  4. iOpus Private Internet Gateway [Windows] – Creates a secure tunnel that encrypts your inbound and outbound WiFi communications. Protects your privacy on public networks.
  5. LucidLink WiFi Client [Windows] – Simplifies the process of securely connecting to a WiFi network, and warns you when you’re connecting to an insecure network.
  6. AirTrafficControl [Mac] – Monitors your WiFi connection for quality and security.


Encryption is a must for the most sensitive types of data. After all, we all know what happens when a password or credit card number winds up in the wrong persons hands. That’s why we recommend you check out a few of the following encryption apps.

  1. Pastor [Mac] – Simple tool used to securely store all of your usernames and passwords.
  2. Access Manager [Windows] – Stores all of your sensitive passwords and personal information into one secure file.
  3. RememberMe [Windows] – Stores your usernames and passwords in an 128-bit AES encrypted file.
  4. Kruptos 2 [Windows] – Integrates into windows right click menus to encrypt and archives files easily.
  5. Crypt4Free [Windows] – Uses Blowfish and DESX encryption to protect your files and create encrypted messages for instant messaging and email clients.
  6. PicSecret [Web, Mac] – Neat feature that allows you to send encrypted messages disguised as ordinary pictures.
  7. GNU Privacy Guard [Windows, Linux, Mac] – A command line based encryption tool using multiple encryption algorithms including OpenPGP, AES, SHA-1, and more.
  8. TrueCrypt [Windows, Linux] – Creates virtual encrypted drives.


Here are few apps that simply didn’t fit into the categories above. Although they might be unclassified, they all offer a great deal of functionality when it comes to overall system security.

  1. Active Security Monitor [Windows] – Uses a proven system to determine if a user’s system is secure or not.
  2. PreView 1.0 [Windows] – Rates your computer on how vulnerable it is.
  3. PC Security Test [Windows] – Determines the vulnerability of your computer by subjecting it to simulated attacks and malware.
  4. PCPal [Windows] – Detects security vulnerabilities in your system and advises you on how to reduce their risks.
  5. Simple File Shredder [Windows] – Securely and permanently delete files on your computer.
  6. BCWipe [Windows] – Permanently deletes files off of your computer.
  7. Permanent Eraser [Mac] – Permanently delete files from your hard drive.
  8. S3 Change Explorer [Windows] – Graphically keeps track of the changes made on your system. Useful for determining if a user or file is making unwanted changes to sensitive files.
  9. Process Monitor [Windows] – Microsoft’s solution for monitoring all of the processes running on your computer. Useful for identifying malware instances.
  10. Check Failed Password Attempts [Mac] – Tool used to scan for failed attempts logging into the administrator account.
  11. CheckMate [Mac] – Compares checksums of critical files to determine their integrity before you download them. By comparing checksums you’ll know if you’re getting the right files, or something infected with malware.
  12. Checksum Validator [Mac] – A very simple checksums comparison tool.