| Anti-Virus |
| AMaViS | Mail virus scanner |
| Avast! | Virus protection, with anti-spyware and anti-rootkit software |
| AVG Free | Anti-virus and Anti-spyware software |
| ClamAV | Anti-virus toolkit for e-mail scanning on mail gateways |
| P3Scan | Scans email messages |
| |
| Anti-Malware |
| chkrootkit | Check for signs of a rootkit |
| OSSEC | Rootkit detection |
| Nixory | Anti Spyware program open source for Mozilla Firefox |
| rkhunter | Scans for rootkits, backdoors and possible local exploits |
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Encryption
|
| GnuPG | Encrypt and sign data and communication |
| MailCrypt | Simple interface to public key cryptography with PGP |
| MCrypt | Developer tool for adding a wide range of encryption functions |
| OpenSignature | Digital signature of documents |
| PeaZip | Portable, open source archiving, encryption and file split tool |
| Seahorse | GNOME application for managing encryption keys |
| Steghide | Hide data in various kinds of image- and audio-files |
| Stunnel | Encrypt arbitrary TCP connections inside SSL (Secure Sockets Layer) |
| TrueCrypt | Disk encryption software |
|
| Firewalls / Network Gateways |
| ClarkConnect | Dedicated firewall and Internet server/gateway |
| FireHOL | Stateful iptables packet filtering firewall configurator |
| Firestarter | Visual firewall program
|
| Netfilter | Packet filtering framework |
IPCop
| Linux firewall distribution
|
| ShellTer | Iptables-based firewall |
| Shorewall | High-level tool for configuring Netfilter |
| Untangle | Quality open source alternative to SonicWALL and WatchGuard |
| Turtle Firewall | Firewall configuration project based on Linux 2.4.x/2.6.x and iptables |
| Vuumuur | Powerful firewall manager built on top of iptables |
|
| Intrusion Detection |
| AFICK | Monitor the changes on your filesystems |
| BASE | Web front-end to query and analyze the alerts from a SNORT IDS system |
| Bro | Passively monitors network traffic and looks for suspicious activity |
| Kismet | Wireless network detector, sniffer, and intrusion detection system |
| OSSEC | Open Source Host-based Intrusion Detection System |
| Sguil | Analyst Console for Network Security Monitoring |
| SNARE | System iNtrusion Analysis and Reporting Environment |
| Snort | Network intrusion prevention and detection |
| Snort_inline | Modified version of Snort |
| Tripwire | Provides configuration audit and control features |
| |
| Network Monitoring |
| AIM Sniff | Monitoring and archiving AOL Instant Messenger and MSN messages |
| Argus | Fixed-model Real Time Flow Monitor |
| Nagios | Host and network monitoring tool |
| Nipper | Network Infrastructure Configuration Parser |
| NSAT | Network Security Analysis Tool |
| ntop | Network traffic probe that shows the network usage |
| SEC | Simple Event Correlator |
| SniffDet | Remote Sniffer Detection Tool/Library |
| tcpdump | Network debugging tool |
|
| Network Traffic Analyzer |
| dsniff | Collection of tools for network auditing and penetration testing |
| Ettercap | Multipurpose sniffer/interceptor/logger for switched LAN |
| ngrep | Network grep |
| Kismet | Wireless network detector, sniffer, and intrusion detection system |
| Wireshark | Network protocol analyzer |
|
| Packet Crafting |
| Hping3 | TCP/IP packet assembler/analyzer |
| Nemesis | Packet crafting and injection utility |
| Scapy | Interactive packet manipulation program |
| Yersinia | Network tool to take advantage of weaknesses in network protocols |
|
| Portscanner |
| Angry IP Scanner | Fast and friendly network scanner |
| Knocker | TCP security port scanner |
| Unicornscan | User-land Distributed TCP/IP stack |
| |
| Vulnerability Scanner |
| Nessus | Comprehensive vulnerability scanning software |
| SARA | Third generation security analysis tool that is based on the SATAN model |
| Tiger | Perform a security audit of UNIX systems |
|
| Log File Analyzers |
| AWStats | Advanced web, streaming, ftp or mail server statistics, graphically |
| IPtables Log Analyzer | Analyzes the log output from an iptables firewall |
| tcpreplay | Use previously captured traffic in libpcap format to test network devices |
| tcptrace | Analyze TCP dump files |
| The Webalizer | Web server log file analysis |
|
| Data Removal |
| Darik's Boot and Nuke | Self-contained boot floppy that securely wipes hard disks |
| Wipe | Secure file wiping utility |
|
| Password Management |
| Figaro's PM | GNOME application that allows password to be securely stored |
| KeePassX | Lightweight and easy-to-use password manager |
|
| VPN Tools |
| Poptop | PPTP server solution |
| OpenVPN | Full-featured SSL VPN solution |
| SSL Explorer | Fully-featured, web-based SSL VPN server |
| |
| Forensics |
| ODESSA | Open Digital Evidence Search and Seizure Architecture |
|
| Other Tools |
| Denyhosts | SSH attack prevention |
| iptables | Configure the Netfilter tables, chains, and rules |
| mtr | Network diagnostic tool |
| Netcat | Reads and writes data across network connections |
| Nikto | Web server scanner performing tests against web servers |
| OpenSSH | SSH connectivity tools |
| Smart Sign | Smartcard based digital signature |