Note: These are archived 2000 survey results. For the latest survey, visit http://SecTools.Org.
In May/June of 2000, we conducted a survey of 1200 Nmap users from the nmap-hackers mailing list to
determine their favorite security tools. Each respondant
could list up to 5.
I was so impressed by the list they created that I am putting the
top 50 up here where everyone can benefit from them. I
think anyone in the security field would be well advised to go over the
list and investigate any tools they are unfamiliar with. I also plan
to point newbies to this page whenever they write me saying "I do not
know where to start".
Respondants were allowed to list open source or commercial tools on
any platform. Commercial tools are noted as such in the list below.
Note that many of the descriptions in this list were taken from the Debian package descriptions, the Freshmeat descriptions, or from the home pages of the application. I didn't count any votes for Nmap because the survey was taken on an Nmap mailing list.
Without further ado, here is the list (starting with the most
Description: Remote network security auditor, the client The Nessus Security Scanner is a security auditing tool. It makes
possible to test security modules in an attempt to find vulnerable
spots that should be fixed. . It is made up of two parts: a server,
and a client. The server/daemon, nessusd, is in charge of the
attacks, whereas the client, nessus, interferes with the user through
nice X11/GTK+ interface. . This package contains the GTK+ 1.2
client, which exists in other forms and on other platforms, too.
Note: This is an unofficial site Description: TCP/IP swiss army knife A simple Unix utility which reads and writes data across network
connections using TCP or UDP protocol. It is designed to be a reliable
"back-end" tool that can be used directly or easily driven by other
programs and scripts. At the same time it is a feature-rich network
debugging and exploration tool, since it can create almost any kind of
connection you would need and has several interesting built-in
Description: A powerful tool for network monitoring and data acquisition This program allows you to dump the traffic on a network. It can
be used to print out the headers of packets on a network interface
that matches a given expression. You can use this tool to track down
network problems, to detect "ping attacks" or to monitor the network
Description: flexible packet sniffer/logger that detects attacks Snort is a libpcap-based packet sniffer/logger which can be used as a
lightweight network intrusion detection system. It features rules
based logging and can perform content searching/matching in addition
to being used to detect a variety of other attacks and probes, such
as buffer overflows, stealth port scans, CGI attacks, SMB probes, and
much more. Snort has a real-time alerting capability, with alerts being
sent to syslog, a separate "alert" file, or even to a Windows computer
Description: SAINT (Security Administrator's Integrated Network Tool) is a security assesment tool based on SATAN. Features include
scanning through a firewall, updated security checks from CERT &
CIAC bulletins, 4 levels of severity (red, yellow, brown, & green)
and a feature rich HTML interface.
Description: Network traffic analyzer Ethereal is a network traffic analyzer, or "sniffer", for Unix and
Unix-like operating systems. It uses GTK+, a graphical user interface
library, and libpcap, a packet capture and filtering library.
Description: Portscan detection daemon PortSentry has the ability to detect portscans(including stealth scans) on
the network interfaces of your machine. Upon alarm it can block the attacker
via hosts.deny, dropped route or firewall rule. It is part of the Abacus
Note: If you have no idea what a port/stealth scan is, I'd recommend to have
a look at http://www.psionic.com/products/portsentry.html before installing this
package. Otherwise you might easily block hosts you'd better not(e.g. your
NFS-server, name-server, ...).
Note: Depending on usage, this tool may have expensive licensing fees associated with it.
Description: A file and directory integrity checker. Tripwire is a tool that aids system administrators and users in
monitoring a designated set of files for any changes. Used with
system files on a regular (e.g., daily) basis, Tripwire can notify
system administrators of corrupted or tampered files, so damage
control measures can be taken in a timely manner.
Description: hping2 is a network tool able to send custom ICMP/UDP/TCP packets and to display target replies like ping does with ICMP
replies. It handles fragmentation and arbitrary packet body and
size, and can be used to transfer files under supported
protocols. Using hping2, you can: test firewall rules, perform
[spoofed] port scanning, test net performance using different
protocols, packet size, TOS (type of service), and fragmentation,
do path MTU discovery, tranfer files (even between really Fascist
firewall rules), perform traceroute-like actions under different
protocols, fingerprint remote OSs, audit a TCP/IP stack,
etc. hping2 is a good tool for learning TCP/IP.
Description: The Security Auditor's Research Assistant (SARA) is a third generation security analysis tool that is based on the SATAN
model which is covered by the GNU GPL-like open license. It is
fostering a collaborative environment and is updated periodically
to address latest threats.
Description: packet sniffer and monitoring tool sniffit is a packet sniffer for TCP/UDP/ICMP packets.
sniffit is able to give you very detailed technical info
on these packets (SEC, ACK, TTL, Window, ...) but also
packet contents in different formats (hex or plain text,
Description: Security Auditing Tool for Analysing Networks This is a powerful tool for analyzing networks for vulnerabilities
created for sysadmins that cannot keep a constant look at bugtraq,
rootshell and the like.
Description: IP Filter is a TCP/IP packet filter, suitable for use in a firewall environment. To use, it can either be used as a loadable kernel module or incorporated into your UNIX kernel; use as a loadable kernel module where possible is highly recommended. Scripts are provided to install and
patch system files, as required.
Description: IP packet filter administration for 2.4.X kernels Iptables is used to set up, maintain, and inspect the
tables of IP packet filter rules in the Linux kernel.
The iptables tool also supports configuration of dynamic and static
network address translation.
Description: Firewalking is a technique developed by MDS and DHG that employs traceroute-like techniques to analyze IP packet responses
to determine gateway ACL filters and map networks. Firewalk the
tool employs the technique to determine the filter rules in place
on a packet forwarding device. The newest version of the tool,
firewalk/GTK introduces the option of using a graphical interface
and a few bug fixes.
Note: No source code is included (except in research version) and there is a $100 registration fee. Description: L0phtCrack is an NT password auditting tool. It will compute NT user passwords from the cryptographic hashes that are
stored by the NT operation system. L0phtcrack can obtain the hashes
through many sources (file, network sniffing, registry, etc) and it
has numerous methods of generating password guesses (dictionary, brute
Description: Advanced packet sniffer and connection intrusion. Hunt is a program for intruding into a connection, watching it and
Note that hunt is operating on Ethernet and is best used for connections
which can be watched through it. However, it is possible to do something
even for hosts on another segments or hosts that are on switched ports.
Note: The ssh.com version cost money for some uses, but source code is available. Description: Secure rlogin/rsh/rcp replacement (OpenSSH) OpenSSH is derived from OpenBSD's version of ssh, which was in turn
derived from ssh code from before the time when ssh's license was
changed to be non-free.
Ssh (Secure Shell) is a program for logging into a remote machine
and for executing commands on a remote machine.
It provides secure encrypted communications between two untrusted
hosts over an insecure network. X11 connections and arbitrary TCP/IP
ports can also be forwarded over the secure channel.
It is intended as a replacement for rlogin, rsh and rcp, and can be
used to provide rdist, and rsync with a secure communication channel.
Description: Wietse Venema's TCP wrappers library Wietse Venema's network logger, also known as TCPD or LOG_TCP.
These programs log the client host name of incoming telnet,
ftp, rsh, rlogin, finger etc. requests. Security options are:
access control per host, domain and/or service; detection of
host name spoofing or host address spoofing; booby traps to
implement an early-warning system.
Description: display network usage in top-like format ntop is a Network Top program. It displays a summary of network usage by
machines on your network in a format reminicent of the unix top utility.
It can also be run in web mode, which allows the display to be browsed with
a web browser.
Note: This is an unofficial download site. Description: The NetBIOS Auditing Tool (NAT) is designed to explore the NETBIOS file-sharing services offered by the target system. It
implements a stepwise approach to gather information and attempt to
obtain file system-level access as though it were a legitimate local
Note: Source code was once freely available but I do not know if this is still the case. Some usage may cost money. Description: A commercial sniffing application for creating intrusion detection systems. Source code was at one time available, but I do
not know if that is still the case.
Description: Mails anomalies in the system logfiles to the administrator Logcheck is part of the Abacus Project of security tools. It is a program
created to help in the processing of UNIX system logfiles generated by the
various Abacus Project tools, system daemons, Wietse Venema's TCP Wrapper
and Log Daemon packages, and the Firewall Toolkit by Trusted Information
Logcheck helps spot problems and security violations in your logfiles
automatically and will send the results to you in e-mail. This program is
free to use at any site. Please read the disclaimer before you use any of
Description: A very powerful scripting language which is often used to create "exploits" for the purpose of verifying security vulnerabilities. Of course, it is also used for all sorts of other things.
Description: grep for network traffic ngrep strives to provide most of GNU grep's common features,
applying them to the network layer. ngrep is a pcap-aware tool that
will allow you to specify extended regular expressions to match
against data payloads of packets. It currently recognizes TCP, UDP
and ICMP across Ethernet, PPP, SLIP and null interfaces, and
understands bpf filter logic in the same fashion as more common
packet sniffing tools, such as tcpdump and snoop.
Description: Vetescan is a bulk vulnerability scanner which contains programs to check for and/or exploit many remote network security
exploits that are known for Windows or UNIX. It includes various
programs for doing different kinds of scanning. Fixes for
vulnerablities are included along with the exploits.
Description: Routines for the construction and handling of network packets. libnet provides a portable framework for low-level network packet writing and
Libnet features portable packet creation interfaces at the IP layer and link
layer, as well as a host of supplementary functionality. Still in it's
infancy however, the library is evolving quite a bit. Additional functionality
and stability are added with each release.
Using libnet, quick and simple packet assembly applications can be whipped up
with little effort. With a bit more time, more complex programs can be written
(Traceroute and ping were easily rewritten using libnet and libpcap).
Description: Crack 5 is an update version of Alec Muffett's classic local password cracker. Traditionally these allowed any user of a
system to crack the /etc/passwd and determine the passwords of other
users (or root) on the system. Modern systems require you to obtain
read access to /etc/shadow in order to perform this. It is still a good idea for sysadmins to run a cracker occasionally to verify that all users have strong passwords.
Description: CIS is a free security scanner written and maintained by Cerberus Information Security, Ltd and is designed to help
administrators locate and fix security holes in their computer
systems. Runs on Windows NT or 2000. No source code is
Description: Swatch was originally written to actively monitor messages as they were written to a log file via the UNIX syslog
utility. It has multiple methods of alarming, both visually and by
triggering events. The perfect tools for a master loghost. This is
a beta release of version 3.0, so please use it with caution. The
code is still slightly ahead of the documentation, but examples
exist. NOTE: Works flawlessly on Linux (RH5), BSDI and Solaris 2.6
Description: The OpenBSD project produces a FREE, multi-platform 4.4BSD-based UNIX-like operating system. Our efforts place emphasis
on portability, standardization, correctness, security, and
cryptography. OpenBSD supports binary emulation of most programs
from SVR4 (Solaris), FreeBSD, Linux, BSDI, SunOS, and HPUX.
Description: The Nemesis Project is designed to be a commandline-based, portable human IP stack for UNIX/Linux. The suite
is broken down by protocol, and should allow for useful scripting of
injected packet streams from simple shell scripts.
Description: List open files. Lsof is a Unix-specific diagnostic tool. Its name stands
for LiSt Open Files, and it does just that. It lists
information about any files that are open by processes
current running on the system.
The binary is specific to kernel version 2.2
Description: The LIDS is an intrusion detection/defense system in the Linux kernel. The goal is to protect linux systems against root
intrusions, by disabling some system calls in the kernel itself. As
you sometimes need to administrate the system, you can disable LIDS
Description: Interactive Colorful IP LAN Monitor IPTraf is an ncurses-based IP LAN monitor that generates
various network statistics including TCP info, UDP counts,
ICMP and OSPF information, Ethernet load info, node stats,
IP checksum errors, and others.
Note that since 2.0.0 IPTraf requires a kernel >= 2.2
Description: iplog is a TCP/IP traffic logger. Currently, it is capable of logging TCP, UDP and ICMP traffic. iplog 2.0 is a
complete re-write of iplog 1.x, resulting in greater portability
and better performance. iplog 2.0 contains all the features of
iplog 1.x as well as several new ones. Major new features include a
packet filter and detection of more scans and attacks. It currently
runs on Linux, FreeBSD, OpenBSD, BSDI and Solaris. Ports to other
systems, as well as any contributions at all, are welcome at this
Description: Fragrouter is aimed at testing the correctness of a NIDS,according to the specific TCP/IP attacks listed in the Secure Networks
NIDS evasion paper.  Other NIDS evasion toolkits which implement
these attacks are in circulation among hackers or publically
available, and it is assumed that they are currently being used to
Note: A couple of the OS detection tests in Queso were later incorporated into Nmap. A paper we wrote on OS detection is available here. Description: Guess the operating system of a remote machine by looking in the TCP replies.
Description: The GNU Privacy Guard (GnuPG) is a complete and free replacement for PGP, developed in Europe. Because it does not use
IDEA or RSA it can be used without any restrictions. GnuPG is a
RFC2440 (OpenPGP) compliant application. PGP is the famous
encryption program which helps secure your data from eavesdroppers
and other risks.