80 of the Best Linux Security Applications

Security is paramount. Security involves defense in depth. Approaching security one step at a time, with consistency and rigour, you can mitigate threats, and keep intruders at bay.

Intruders use a variety of different techniques in an attempt to compromise a system. For example, systems can be attacked by denial of service, cracking, intrusion, snooping (intercepting the data of another user), or viruses/worms/Trojan horses. To have a secure box, a system therefore needs a variety of defenses.

The aim of this article is to provide the user with a starting point for improving the security of a Linux machine. Basic system security (e.g. having a regular backup strategy, using hard-to-guess passwords, removing services that you don’t need) is essential administration in protecting your data. But you need a more sophisticated approach to keep intruders out.

We have identified 80 of the best Linux security applications which help to protect the integrity of a system. For each application we have compiled its own portal page, providing a detailed description of the software, its features, with links to other relevant resources.

All of the software featured in this article is free to download, and almost all released under the GNU General Public License.

Security Applications
AMaViSMail virus scanner
Avast!Virus protection, with anti-spyware and anti-rootkit software
AVG FreeAnti-virus and Anti-spyware software
ClamAV IRCAnti-virus toolkit for e-mail scanning on mail gateways
P3ScanScans email messages
chkrootkitCheck for signs of a rootkit
OSSECRootkit detection
NixoryAnti Spyware program open source for Mozilla Firefox
rkhunterScans for rootkits, backdoors and possible local exploits
GnuPGEncrypt and sign data and communication
MailCryptSimple interface to public key cryptography with PGP
MCryptDeveloper tool for adding a wide range of encryption functions
OpenSignatureDigital signature of documents
PeaZipPortable, open source archiving, encryption and file split tool
SeahorseGNOME application for managing encryption keys
SteghideHide data in various kinds of image- and audio-files
StunnelEncrypt arbitrary TCP connections inside SSL (Secure Sockets Layer)
TrueCryptDisk encryption software
ClearOSDedicated firewall and Internet server/gateway
FireHOLStateful iptables packet filtering firewall configurator
FirestarterVisual firewall program
NetfilterPacket filtering framework
IPCopLinux firewall distribution
ShellTerIptables-based firewall
ShorewallHigh-level tool for configuring Netfilter
UntangleQuality open source alternative to SonicWALL and WatchGuard
Turtle FirewallFirewall configuration project based on Linux 2.4.x/2.6.x and iptables
VuumuurPowerful firewall manager built on top of iptables
AFICKMonitor the changes on your filesystems
BASEWeb front-end to query and analyze the alerts from a SNORT IDS system
BroPassively monitors network traffic and looks for suspicious activity
KismetWireless network detector, sniffer, and intrusion detection system
OSSECHost-based Intrusion Detection System
SguilAnalyst Console for Network Security Monitoring
SNARESystem iNtrusion Analysis and Reporting Environment
SnortNetwork intrusion prevention and detection
Snort_inlineModified version of Snort
TripwireProvides configuration audit and control features
AIM SniffMonitoring and archiving AOL Instant Messenger and MSN messages
ArgusFixed-model Real Time Flow Monitor
NagiosHost and network monitoring tool
NipperNetwork Infrastructure Configuration Parser
NSATNetwork Security Analysis Tool
ntopNetwork traffic probe that shows the network usage
SECSimple Event Correlator
SniffDetRemote Sniffer Detection Tool/Library
tcpdumpNetwork debugging tool
dsniffCollection of tools for network auditing and penetration testing
EttercapMultipurpose sniffer/interceptor/logger for switched LAN
ngrepNetwork grep
KismetWireless network detector, sniffer, and intrusion detection system
WiresharkNetwork protocol analyzer
Hping3TCP/IP packet assembler/analyzer
NemesisPacket crafting and injection utility
ScapyInteractive packet manipulation program
YersiniaNetwork tool to take advantage of weaknesses in network protocols
Angry IP ScannerFast and friendly network scanner
KnockerTCP security port scanner
UnicornscanUser-land Distributed TCP/IP stack
NessusComprehensive vulnerability scanning software
SARAThird generation security analysis tool that is based on the SATAN model
TigerPerform a security audit of UNIX systems
AWStatsAdvanced web, streaming, ftp or mail server statistics, graphically
IPtables Log AnalyzerAnalyzes the log output from an iptables firewall
tcpreplayUse previously captured traffic in libpcap format to test network devices
tcptraceAnalyze TCP dump files
The WebalizerWeb server log file analysis
Darik's Boot and NukeSelf-contained boot floppy that securely wipes hard disks
WipeSecure file wiping utility
Figaro's PMGNOME application that allows password to be securely stored
KeePassX Lightweight and easy-to-use password manager
PoptopPPTP server solution
OpenVPNFull-featured SSL VPN solution
SSL ExplorerFully-featured, web-based SSL VPN server
ODESSAOpen Digital Evidence Search and Seizure Architecture
DenyhostsSSH attack prevention
iptablesConfigure the Netfilter tables, chains, and rules
mtrNetwork diagnostic tool
NetcatReads and writes data across network connections
NiktoWeb server scanner performing tests against web servers
OpenSSHSSH connectivity tools
Smart SignSmartcard based digital signature

Read our complete collection of recommended free and open source software. The collection covers all categories of software.

The software collection forms part of our series of informative articles for Linux enthusiasts. There's tons of in-depth reviews, open source alternatives to proprietary software from large corporations like Google, Microsoft, Apple, Adobe, Corel, and Autodesk. There are also fun things to try, hardware, free programming books and tutorials, and much more.
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