GptAdmin : Business : Network

Network security systems protect networks and their services from unauthorized modification, destruction, or disclosure, and assures that the network performs its critical functions correctly. Network security is essential for business that rely on computer systems. Proper safeguarding of everything associated with a network, including data, media, and equipment is vital for companies to function effectively in globally integrated business environments. Companies that provide network security provide administrative functions, such as threat assessment, technical tools and facilities, such as cryptographic products, and network access control products, such as firewalls. They will also make certain that network resources are used in accordance with a prescribed policy and only by people who are authorized to use these resources. Network security also includes providing for data integrity.

There are many companies providing Network Security solutions; those listed on this page are some of the leaders in the industry.

Sites:

» Achilles: A Windows web attack proxy -

Achilles is a tool designed for testing the security of web applications. Achilles is a proxy server, which acts as a man-in-the-middle during an HTTP session. A typical HTTP proxy will relay packets to and from a client browser and a web server. Achilles will intercept an HTTP session's data in either direction and give the user the ability to alter the data before transmission. For example, during a normal HTTP SSL connection a typical proxy will relay the session between the server and the client and allow the two end nodes to negotiate SSL. In contrast, when in intercept mode, Achilles will pretend to be the server and negotiate two SSL sessions, one with the client browser and another with the web server. As data is transmitted between the two nodes, Achilles decrypts the data and gives the user the ability to alter and/or log the data in clear text before transmission.

» AirSnort: 802.11 WEP Encryption Cracking Tool -

AirSnort is a wireless LAN (WLAN) tool that recovers encryption keys. It was developed by the Shmoo Group and operates by passively monitoring transmissions, computing the encryption key when enough packets have been gathered. Windows support is still very preliminary.

» Brutus: A network brute-force authentication cracker -

This Windows-only cracker bangs against network services of remote systems trying to guess passwords by using a dictionary and permutations thereof. It supports HTTP, POP3, FTP, SMB, TELNET, IMAP, NTP, and more. No source code is available. UNIX users should take a look at THC-Hydra.

» Cain & Abel: The poor man's L0phtcrack -

Cain & Abel is a free password recovery tool for Microsoft Operating Systems. It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary & Brute-Force attacks, decoding scrambled passwords, revealing password boxes, uncovering cached passwords and analyzing routing protocols. Source code is not provided.

» DSniff: A suite of powerful network auditing and penetration-testing tools -

This popular and well-engineered suite by Dug Song includes many tools. dsniff, filesnarf, mailsnarf, msgsnarf, urlsnarf, and webspy passively monitor a network for interesting data (passwords, e-mail, files, etc.). arpspoof, dnsspoof, and macof facilitate the interception of network traffic normally unavailable to an attacker (e.g, due to layer-2 switching). sshmitm and webmitm implement active monkey-in-the-middle attacks against redirected SSH and HTTPS sessions by exploiting weak bindings in ad-hoc PKI. A separately maintained partial Windows port is available here.

» Ethereal: Sniffing the glue that holds the Internet together -

Ethereal is a free network protocol analyzer for Unix and Windows. It allows you to examine data from a live network or from a capture file on disk. You can interactively browse the capture data, viewing summary and detail information for each packet. Ethereal has several powerful features, including a rich display filter language and the ability to view the reconstructed stream of a TCP session. A text-based version called tethereal is included.

» Ettercap: In case you still thought switched LANs provide much extra security -

Ettercap is a terminal-based network sniffer/interceptor/logger for ethernet LANs. It supports active and passive dissection of many protocols (even ciphered ones, like SSH and HTTPS). Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized. Many sniffing modes were implemented to give you a powerful and complete sniffing suite. Plugins are supported. It has the ability to check whether you are in a switched LAN or not, and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.

» Firewalk: Advanced traceroute -

Firewalk employs traceroute-like techniques to analyze IP packet responses to determine gateway ACL filters and map networks. This classic tool was rewritten from scratch in October 2002. Note that much or all of this functionality can also be performed by the Hping2 --traceroute option.

» Fport: Foundstone's enhanced netstat -

fport reports all open TCP/IP and UDP ports on the machine you run it on and shows what application opened each port. So it can be used to quickly identify unknown open ports and their associated applications. It only runs on Windows, but many UNIX systems now provided this information via netstat (try 'netstat -pan' on Linux). Here is a PDF-Format SANS article on using Fport and analyzing the results.

» Fragroute: IDS systems' worst nightmare -

Fragroute intercepts, modifies, and rewrites egress traffic, implementing most of the attacks described in the Secure Networks IDS Evasion paper. It features a simple ruleset language to delay, duplicate, drop, fragment, overlap, print, reorder, segment, source-route, or otherwise monkey with all outbound packets destined for a target host, with minimal support for randomized or probabilistic behaviour. This tool was written in good faith to aid in the testing of intrusion detection systems, firewalls, and basic TCP/IP stack behaviour. Like Dsniff, and Libdnet, this excellent tool was written by Dug Song.

» GFI LANguard: A commercial network security scanner for Windows -

LANguard scans networks and reports information such as service pack level of each machine, missing security patches, open shares, open ports, services/applications active on the computer, key registry entries, weak passwords, users and groups, and more. Scan results are outputted to an HTML report, which can be customized/queried. Apparently a limited free version is available for non-commercial/trial use.

» GnuPG: Secure your files and communication w/advanced encryption -

PGP is the famous encryption program by Phil Zimmerman which helps secure your data from eavesdroppers and other risks. GnuPG is a very well-regarded open source implentation of the PGP standard (the actual executable is named gpg). While GnuPG is always free, PGP costs money for some uses.

» Home Network Security -

What is computer security?

Computer security is the process of preventing and detecting unauthorized use of your computer. Prevention measures help you to stop unauthorized users (also known as "intruders") from accessing any part of your computer system. Detection helps you to determine whether or not someone attempted to break into your system, if they were successful, and what they may have done.

Why should I care about computer security?

We use computers for everything from banking and investing to shopping and communicating with others through email or chat programs. Although you may not consider your communications "top secret," you probably do not want strangers reading your email, using your computer to attack other systems, sending forged email from your computer, or examining personal information stored on your computer (such as financial statements).

Who would want to break into my computer at home?

Intruders (also referred to as hackers, attackers, or crackers) may not care about your identity. Often they want to gain control of your computer so they can use it to launch attacks on other computer systems.

Having control of your computer gives them the ability to hide their true location as they launch attacks, often against high-profile computer systems such as government or financial systems. Even if you have a computer connected to the Internet only to play the latest games or to send email to friends and family, your computer may be a target.

Intruders may be able to watch all your actions on the computer, or cause damage to your computer by reformatting your hard drive or changing your data.

How easy is it to break into my computer?

Unfortunately, intruders are always discovering new vulnerabilities (informally called "holes") to exploit in computer software. The complexity of software makes it increasingly difficult to thoroughly test the security of computer systems.

When holes are discovered, computer vendors will usually develop patches to address the problem(s). However, it is up to you, the user, to obtain and install the patches, or correctly configure the software to operate more securely. Most of the incident reports of computer break-ins received at the CERT/CC could have been prevented if system administrators and users kept their computers up-to-date with patches and security fixes.

Also, some software applications have default settings that allow other users to access your computer unless you change the settings to be more secure. Examples include chat programs that let outsiders execute commands on your computer or web browsers that could allow someone to place harmful programs on your computer that run when you click on them.

» Honeyd: Your own personal honeynet -

Honeyd is a small daemon that creates virtual hosts on a network. The hosts can be configured to run arbitrary services, and their TCP personality can be adapted so that they appear to be running certain versions of operating systems. Honeyd enables a single host to claim multiple addresses on a LAN for network simulation. It is possible to ping the virtual machines, or to traceroute them. Any type of service on the virtual machine can be simulated according to a simple configuration file. It is also possible to proxy services to another machine rather than simulating them. The web page is currently down for legal reasons, but the V. 0.5 tarball is still available here.

» Hping2: A network probing utility like ping on steroids -

hping2 assembles and sends custom ICMP/UDP/TCP packets and displays any replies. It was inspired by the ping command, but offers far more control over the probes sent. It also has a handy traceroute mode and supports IP fragmentation. This tool is particularly useful when trying to traceroute/ping/probe hosts behind a firewall that blocks attempts using the standard utilities.

» Hunt: An advanced packet sniffing and connection intrusion tool for Linux -

Hunt can watch TCP connections, intrude into them, or reset them. Hunt is meant to be used on ethernet, and has active mechanisms to sniff switched connections. Advanced features include selective ARP relaying and connection synchronization after attacks. If you like Hunt, also take a look at Ettercap and Dsniff.

» ISS Internet Scanner: Application-level vulnerability assessment -

Internet Scanner started off in '92 as a tiny Open Source scanner by Christopher Klaus. Now he has grown ISS into a billion-dollar company with a myriad of security products. ISS Internet Scanner is pretty good, but is not cheap. So companies on a tight budget may wish to look at Nessus instead. A March 2003 Information Security magazine review of 5 VA tools (including these) is available here. Note that VA tools only report vulnerabilities. Commercial tools for actually exploiting them include CORE Impact and Dave Aitel's Canvas. Free exploits for some vulnerabilities can be found at sites like Packet Storm and SecurityFocus

» Introduction to Network Security -

Introduction to Network Security

Matt Curtin

March 1997

Reprinted with the permission of Kent Information Services, Inc.

(Also available in Postscript and PDF formats for those who prefer, and nicer hardcopy.)

Abstract:

Network security is a complicated subject, historically only tackled by well-trained and experienced experts. However, as more and more people become ``wired'', an increasing number of people need to understand the basics of security in a networked world. This document was written with the basic computer user and information systems manager in mind, explaining the concepts needed to read through the hype in the marketplace and understand risks and how to deal with them.

Some history of networking is included, as well as an introduction to TCP/IP and internetworking . We go on to consider risk management, network threats, firewalls, and more special-purpose secure networking devices.

This is not intended to be a ``frequently asked questions'' reference, nor is it a ``hands-on'' document describing how to accomplish specific functionality.

It is hoped that the reader will have a wider perspective on security in general, and better understand how to reduce and manage risk personally, at home, and in the workplace.

» John the Ripper: An extraordinarily powerful, flexible, and fast multi-platform password hash cracker -

John the Ripper is a fast password cracker, currently available for many flavors of Unix (11 are officially supported, not counting different architectures), DOS, Win32, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types which are most commonly found on various Unix flavors, as well as Kerberos AFS and Windows NT/2000/XP LM hashes. Several other hash types are added with contributed patches.

» Kismet: A powerful wireless sniffer -

Kismet is an 802.11b network sniffer and network dissector. It is capable of sniffing using most wireless cards, automatic network IP block detection via UDP, ARP, and DHCP packets, Cisco equipment lists via Cisco Discovery Protocol, weak cryptographic packet logging, and Ethereal and tcpdump compatible packet dump files. It also includes the ability to plot detected networks and estimated network ranges on downloaded maps or user supplied image files. Windows support is currently preliminary, so those users may want to look at Netstumbler if they run into trouble. Linux (and Linux PDAs like Zaurus) users may wish to also look at the Wellenreiter wireless scanner.

» L0phtCrack 4 (now called "LC4"): Windows password auditing and recovery application -

L0phtCrack attempts to crack Windows passwords from hashes which it can obtain (given proper access) from stand-alone Windows NT/2000 workstations, networked servers, primary domain controllers, or Active Directory. In some cases it can sniff the hashes off the wire. It also has numerous methods of generating password guesses (dictionary, brute force, etc). L0phtcrack currently costs $350/machine and no source code is provided. Companies on a tight budget may want to look at John the Ripper, Cain & Abel, and pwdump3.

» LSOF: LiSt Open Files -

This Unix-specific diagnostic and forensics tool lists information about any files that are open by processes currently running on the system. It can also list communications sockets open by each process.

» N-Stealth: Web server scanner -

N-Stealth is a commercial web server security scanner. It is generally updated more frequently than free web scanners such as whisker and nikto, but do take their web site with a grain of salt. The claims of "30,000 vulnerabilities and exploits" and "Dozens of vulnerability checks are added every day" are highly questionable. Also note that essentially all general VA tools such as nessus, ISS, Retina, SAINT, and SARA include web scanning components. They may not all be as up-to-date or flexible though. N-stealth is Windows only and no source code is provided.

» NBTScan: Gathers NetBIOS info from Windows networks -

NBTscan is a program for scanning IP networks for NetBIOS name information. It sends NetBIOS status query to each address in supplied range and lists received information in human readable form. For each responded host it lists IP address, NetBIOS computer name, logged-in user name and MAC address.

» NGrep: Convenient packet matching & display -

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 or hexadecimal expressions to match against data payloads of packets. It currently recognizes TCP, UDP and ICMP across Ethernet, PPP, SLIP, FDDI, Token Ring and null interfaces, and understands bpf filter logic in the same fashion as more common packet sniffing tools, such as tcpdump and snoop.

» NTop: A network traffic usage monitor -

Ntop shows network usage in a way similar to what top does for processes. In interactive mode, it displays the network status on the user's terminal. In Web mode, it acts as a Web server, creating an HTML dump of the network status. It sports a NetFlow/sFlow emitter/collector, an HTTP-based client interface for creating ntop-centric monitoring applications, and RRD for persistently storing traffic statistics.

» Nemesis: Packet injection simplified -

The Nemesis Project is designed to be a commandline-based, portable human IP stack for UNIX/Linux (and now Windows!). The suite is broken down by protocol, and should allow for useful scripting of injected packet streams from simple shell scripts. If you enjoy Nemesis, you might also want to look at hping2. They complement each other well.

» Nessus: The premier Open Source vulnerability assessment tool -

Nessus is a remote security scanner for Linux, BSD, Solaris, and other Unices. It is plug-in-based, has a GTK interface, and performs over 1200 remote security checks. It allows for reports to be generated in HTML, XML, LaTeX, and ASCII text, and suggests solutions for security problems.

» Netcat: The network 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 capabilities.

» Network Security Library -

Welcome to the Secinf.net Network Security Library! Use this site to access hundreds of articles, FAQs, white papers and books on network security, gathered from various sources throughout the industry.

You can help us build the largest free security library on the Internet by submitting your own security-related content and suggestions to content@WindowSecurity.com. We look forward to hearing from you!

» Network Security Scanner & Port Scanner -

Automatically detect security

vulnerabilities on your network

GFI LANguard Network Security Scanner (N.S.S.) checks your network for all potential methods that a hacker might use to attack it. By analyzing the operating system and the applications running on your network, GFI LANguard N.S.S. identifies possible security holes. In other words, it plays the devil's advocate and alerts you to weaknesses before a hacker can find them, enabling you to deal with these issues before a hacker can exploit them.

Provides in-depth information about all

machines/devices

GFI LANguard N.S.S. scans your entire network, IP by IP, and provides information such as service pack level of the machine, missing security patches, wireless access points, USB devices, open shares, open ports, services/applications active on the computer, key registry entries, weak passwords, users and groups, and more. Scan results can easily be analyzed using filters and reports, enabling you to proactively secure your network - for example, by shutting down unnecessary ports, closing shares, installing service packs and hotfixes, etc.

Patch management

GFI LANguard N.S.S. is also a complete patch management solution. After it has scanned your network and determined missing patches and service packs - both in the operating system and in the applications - you can use GFI LANguard N.S.S. to deploy those service packs and patches network-wide. It can also deploy custom software network-wide.

» Network Stumbler: Free Windows 802.11 Sniffer -

Netstumbler is the best known Windows tool for finding open wireless access points ("wardriving"). They also distribute a WinCE version for PDAs and such called Ministumbler. The tool is currently free but Windows-only and no source code is provided. They note that "the author reserves the right to change this license agreement as he sees fit, without notice." UNIX users (and advanced Win users) may want to look at Kismet instead.

» Nikto: A more comprehensive web scanner -

Nikto is a web server scanner which looks for over 2000 potentially dangerous files/CGIs and problems on over 200 servers. It uses LibWhisker but is generally updated more frequently than Whisker itself.

» OpenSSH : A secure way to access remote computers -

Ssh (Secure Shell) is a program for logging into or 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. OpenSSH is affiliated with the OpenBSD project, though a portable version runs on most UNIX systems. Note that the SSH.Com link above costs money for some uses, while OpenSSH is always free. Windows users may want to try the free PuTTY SSH Client or the nice terminal-based port of OpenSSH that comes with Cygwin. There are dozens of other clients (free or prorietary) available for most platforms - here is a huge list.

» OpenSSL: The premier SSL/TLS encryption library -

The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, full-featured, and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library. The project is managed by a worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation.

» PGP: Secure your files and communication w/advanced encryption -

PGP is the famous encryption program by Phil Zimmerman which helps secure your data from eavesdroppers and other risks. GnuPG is a very well-regarded open source implentation of the PGP standard (the actual executable is named gpg). While GnuPG is always free, PGP costs money for some uses.

» Paketto Keiretsu: Extreme TCP/IP -

The Paketto Keiretsu is a collection of tools that use new and unusual strategies for manipulating TCP/IP networks. They tap functionality within existing infrastructure and stretch protocols beyond what they were originally intended for. It includes Scanrand, an unusually fast network service and topology discovery system, Minewt, a user space NAT/MAT router, linkcat, which presents a Ethernet link to stdio, Paratrace, which traces network paths without spawning new connections, and Phentropy, which uses OpenQVIS to render arbitrary amounts of entropy from data sources in three dimensional phase space. Got all that? :).

» Perl: Portable, general-purpose scripting languages -

While many canned security tools are available on this page for handling common tasks, it is important to have the ability to write your own (or modify the existing ones) when you need something more custom. Perl and Python make it very easy to write quick, portable scripts to test, exploit, or even fix systems! Archives like CPAN are filled with modules such as Net::RawIP and protocol implementations to make your tasks even easier.

» Python: Portable, general-purpose scripting languages -

While many canned security tools are available on this page for handling common tasks, it is important to have the ability to write your own (or modify the existing ones) when you need something more custom. Perl and Python make it very easy to write quick, portable scripts to test, exploit, or even fix systems! Archives like CPAN are filled with modules such as Net::RawIP and protocol implementations to make your tasks even easier.

» Retina: Commertial vulnerability assessment scanner by eEye -

Like Nessus and ISS Internet Scanner mentioned previously, Retina's function is to scan all the hosts on a network and report on any vulnerabilities found.

» SAINT: Security Administrator's Integrated Network Tool -

Saint is another commercial vulnerability assessment tool (like ISS Internet Scanner or eEye Retina). Unlike those Windows-only tools, SAINT runs exclusively on UNIX. Saint used to be free and open source, but is now a commercial product.

» SARA: Security Auditor's Research Assistant -

SARA is a vulnerability assessment tool that was derived from the infamous SATAN scanner. They try to release updates twice a month and try to leverage other software created by the open source community (such as Nmap and Samba).

» SPIKE Proxy: HTTP Hacking -

Spike Proxy is an open source HTTP proxy for finding security flaws in web sites. It is part of the Spike Application Testing Suite and supports automated SQL injection detection, web site crawling, login form brute forcing, overflow detection, and directory traversal detection.

» SSH : A secure way to access remote computers -

Ssh (Secure Shell) is a program for logging into or 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. OpenSSH is affiliated with the OpenBSD project, though a portable version runs on most UNIX systems. Note that the SSH.Com link above costs money for some uses, while OpenSSH is always free. Windows users may want to try the free PuTTY SSH Client or the nice terminal-based port of OpenSSH that comes with Cygwin. There are dozens of other clients (free or prorietary) available for most platforms - here is a huge list.

» Sam Spade: Freeware Windows network query tool -

SamSpade provides a consistent GUI and implementation for many handy network query tasks. It was designed with tracking down spammers in mind, but can be useful for many other network exploration, administration, and security tasks. It includes tools such as ping, nslookup, whois, dig, traceroute, finger, raw HTTP web browser, DNS zone transfer, SMTP relay check, website search, and more. Non-Windows users can enjoy online versions of many of their tools.

» Snort: A free intrusion detection system (IDS) for the masses -

Snort is a lightweight network intrusion detection system, capable of performing real-time traffic analysis and packet logging on IP networks. It can perform protocol analysis, content searching/matching and can be used to detect a variety of attacks and probes, such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, and much more. Snort uses a flexible rule based language to describe traffic that it should collect or pass, and a modular detection engine. Many people also suggested that the Analysis Console for Intrusion Databases (ACID) be used with Snort.

» SolarWinds Toolsets: A plethora of network discovery/monitoring/attack tools -

SolarWinds has created and sells dozens of special-purpose tools targetted at systems administrators. Security related tools include many network discovery scanners and an SNMP brute-force cracker. These tools are Windows only, cost money, and do not include source code.

» Stunnel: A general-purpose SSL cryptographic wrapper -

The stunnel program is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote server. It can be used to add SSL functionality to commonly used inetd daemons like POP2, POP3, and IMAP servers without any changes in the programs' code. It will negotiate an SSL connection using the OpenSSL or SSLeay libraries.

» SuperScan: Foundstone's Windows TCP port scanner -

A connect-based TCP port scanner, pinger and hostname resolver. No source code is provided. It can handle ping scans and port scans using specified IP ranges. It can also connect to any discovered open port using user-specified "helper" applications (e.g. Telnet, Web browser, FTP).

» TCPDump / WinDump: The classic sniffer for network monitoring and data acquisition -

Tcpdump is a well-known and well-loved text-based network packet analyzer ("sniffer"). 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 or to monitor network activities. There is a separate Windows port named WinDump. TCPDump is also the source of the Libpcap/WinPcap packet capture library, which is used by Nmap among many other utilities. Note that many users prefer the newer Ethereal sniffer.

» THC-Amap: An application fingerprinting scanner -

Amap (by THC) is a new but powerful scanner which probes each port to identify applications and services rather than relying on static port mapping.

» THC-Hydra: Parallized network authentication cracker -

This tool allows for rapid dictionary attacks against network login systems, including FTP, POP3, IMAP, Netbios, Telnet, HTTP Auth, LDAP NNTP, VNC, ICQ, Socks5, PCNFS, and more. It includes SSL support and is apparently now part of Nessus. Like Amap, this release is from the fine folks at THC.

» Tripwire: The grand-daddy of file integrity checkers -

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. An Open Source Linux version is freely available at Tripwire.Org. UNIX users may also want to consider AIDE, which has been designed to be a free Tripwire replacement. Or you may wish to investigate Radmind.

» Whisker/Libwhisker: Rain.Forest.Puppy's CGI vulnerability scanner and library -

Whisker is a scanner which allows you to test HTTP servers for many known security holes, particularly the presence of dangerous CGIs. Libwhisker is a perl library (used by Whisker) which allows for the creation of custom HTTP scanners. If you wish to audit more than just web servers, have a look at Nessus.

» XProbe2: Active OS fingerprinting tool -

XProbe is a tool for determining the operating system of a remote host. They do this using some of the same techniques as Nmap as well as many different ideas. Xprobe has always emphasized the ICMP protocol in their fingerprinting approach.

» filter: The current Linux kernel packet filter/firewall -

Netfilter is a powerful packet filter which is implemented in the standard Linux kernel. The userspace iptables tool is used for configuration. It now supports packet filtering (stateless or stateful), all different kinds of NAT (Network Address Translation) and packet mangling. For non-Linux platforms, see pf (OpenBSD), ipfilter (many other UNIX variants), or even the Zone Alarm personal firewall (Windows).

Last Updated: 2005-10-27 12:42:57