mind: to break insecure passwords.  It is probably the most efficent andfriendly password cracker that is publically available, with the abilityto let the user to specify precisely how to form the words to use asguesses at users passwords.It also has an inbuilt networking capability, allowing the load ofcracking to be spread over as many machines as are available on anetwork, and it is supplied with an optimised version of the Unix crypt()algorithm.An even faster version of the crypt() algorithm, "UFC" by Michael Glad,is freely available on the network, and the latest versions of UFC andCrack are compatible and can be easily hooked together.3) NPasswd (Clyde Hoover) & Passwd+ (Matt Bishop)These programs are written to redress the balance in the passwordcracking war.  They provide replacements for the standard "passwd"command, but prevent a user from selecting passwords which are easilycompromised by programs like Crack.Several versions of these programs are available on the network, hackedabout to varying degrees in order to provide compatibility for System Vbased systems, NIS/YP, shadow password schemes, etc.  The usual term forthis type of program is a 'fascist' password program.4) "Shadow" - a Shadow Password SuiteThis program suite (by John F Haugh II) is a set of program and functionreplacements (compatible with most Unixes) which implements shadowpasswords, ie: a system where the plaintext of the password file ishidden from all users except root, hopefully stopping all passwordcracking attempts at source.  In combination with a fascist passwdfrontend, it should provide a good degree of password file robustness.>From: jfh@rpp386.lonestar.org (John F. Haugh II)>Shadow does much more than hide passwords.  It also provides for>terminal access control, user and group administration, and a few>other things which I've forgotten.  There are a dozen or more>commands in the suite, plus a whole slew of library functions.5) TCP Wrappers (Wietse Venema)These are programs which provide a front-end filter to many of thenetwork services which Unix provides by default.  If installed, they cancurb otherwise unrestricted access to potential dangers like incomingFTP/TFTP, Telnet, etc, and can provide extra logging information, whichmay be of use if it appears that someone is trying to break in.6) SecureLib>From: phil@pex.eecs.nwu.edu (William LeFebvre)>You may want to add a mention of securelib, a security enhancer>available for SunOS version 4.1 and higher.>Securelib contains replacement routines for three kernel calls:>accept(), recvfrom(), recvmsg().  These replacements are compatible with>the originals, with the additional functionality that they check the>Internet address of the machine initiating the connection to make sure>that it is "allowed" to connect.  A configuration file defines what>hosts are allowed for a given program.  Once these replacement routines>are compiled, they can be used when building a new shared libc library.>The resulting libc.so can then be put in a special place.  Any program>that should be protected can then be started with an alternate>LD_LIBRARY_PATH.7) SPI>From: Gene Spafford <spaf@cs.purdue.edu>>Sites connected with the Department of Energy and some military>organizations may also have access to the SPI package.  Interested (and>qualified) users should contact the CIAC at LLNL for details.>SPI is a screen-based administrator's tool that checks configuration>options, includes a file-change (integrity) checker to monitor for>backdoors and viruses, and various other security checks.  Future>versions will probably integrate COPS into the package.  It is not>available to the general public, but it is available to US Dept of>Energy contractors and sites and to some US military sites.  A version>does or will exist for VMS, too.  Further information on availabilty can>be had from the folks at the DoE CIAC.Q.6 Isn't it dangerous to give cracking tools to everyone?That depends on your point of view.  Some people have complained thatgiving unrestricted public access to programs like COPS and Crack isirresponsible because the "baddies" can get at them easily.Alternatively, you may believe that the really bad "baddies" have hadprograms like this for years, and that it's really a stupendously goodidea to give these programs to the good guys too, so that they may checkthe integrity of their system before the baddies get to them.So, who wins more from having these programs freely available? The goodguys or the bad ? You decide, but remember that less honest tools thanCOPS and Crack tools were already out there, and most of the good guysdidn't have anything to help.Q.7 Where can I get these tools?COPS:  V1.04, available for FTP from cert.sei.cmu.edu in pub/cops and  archive.cis.ohio-state.edu in pub/cops.Crack/UFC:  Crack v4.1f and UFC Patchlevel 1.  Available from any major USENET  archive (eg: ftp.uu.net) in volume 28 of comp.sources.misc.NPasswd:  Currently suffering from being hacked about by many different people.  Version 2.0 is in the offing, but many versions exist in many  different configurations. Will chase this up with authors - AEMPasswd+:  "alpha version, update 3" - beta version due soon.  Available from  dartmouth.edu as pub/passwd+.tar.ZShadow:  This is available from the comp.sources.misc directory at any major  USENET archive (see entry for Crack)TCP Wrappers:  Available for anonymous FTP:    cert.sei.cmu.edu: pub/network_tools/tcp_wrapper.shar    ftp.win.tue.nl: pub/security/log_tcp.shar.ZSecurelib:  The latest version of securelib is available via anonymous FTP from the  host "eecs.nwu.edu".  It is stored in the file "pub/securelib.tar".Q.8 Why and how do systems get broken into?This is hard to answer definitively.  Many systems which crackers breakinto are only used as a means of entry into yet more systems; by hoppingbetween many machines before breaking into a new one, the cracker hopesto confuse any possible pursuers and put them off the scent.  There isan advantage to be gained in breaking into as many different sites aspossible, in order to "launder" your connections.Another reason may be psychological: some people love to play withcomputers and stretch them to the limits of their capabilities.Some crackers might think that it's "really neat" to hop over 6 Internetmachines, 2 gateways and an X.25 network just to knock on the doors ofsome really famous company or institution (eg: NASA, CERN, AT+T, UCB).Think of it as inter-network sightseeing.This view is certainly appealing to some crackers, and certainly leadsto both the addiction and self-perpetuation of cracking.As to the "How" of the question, this is again a very sketchy area.  Inuniversities, it is extremely common for computer account to be passedback and forth between undergraduates:  "Mary gives her account password to her boyfriend Bert at another  site, who has a friend Joe who "plays around on the networks".  Joe  finds other crackable accounts at Marys site, and passes them around  amongst his friends..." pretty soon, a whole society of crackers is  playing around on the machines that Mary uses.This sort of thing happens all the time, and not just in universities.One solution is in education.  Do not let your users develop attitudeslike this one:       "It doesn't matter what password I use on _MY_ account,            after all, I only use it for laserprinting..."                                - an Aberystwyth Law student, 1991Teach them that use of the computer is a group responsibility.  Makesure that they understand that a chain is only as strong as it's weaklink.Finally, when you're certain that they understand your problems as asystems manager and that they totally sympathise with you, configureyour system in such a way that they can't possibly get it wrong.Believe in user education, but don't trust to it alone.Q.9 Who can I contact if I get broken into?If you're connected to the Internet, you should certainly get in touchwith CERT, the Computer Emergency Response Team.        To quote the official blurb:>From: Ed DeHart> The Computer Emergency Response Team (CERT) was formed by the Defense> Advanced Research Projects Agency (DARPA) in 1988 to serve as a focal> point for the computer security concerns of Internet users.  The> Coordination Center for the CERT is located at the Software Engineering> Institute, Carnegie Mellon University, Pittsburgh, PA.> Internet E-mail: cert@cert.sei.cmu.edu> Telephone: 412-268-7090 24-hour hotline:>     CERT/CC personnel answer 7:30a.m. to 6:00p.m. EST(GMT-5)/EDT(GMT-4),>     and are on call for emergencies during other hours....and also, the umbrella group "FIRST", which mediates between theincident handling teams themselves...>From: John Wack <wack@csrc.ncsl.nist.gov>>[...] FIRST is actually a very viable and growing>organization, of which CERT is a member.  It's not actually true that,>if you're connected to the Internet, you should call CERT only - that>doesn't do justice to the many other response teams out there and in the>process of forming.>NIST is currently the FIRST secretariat; we maintain an anonymous ftp>server with a directory of FIRST information (csrc.ncsl.nist.gov:>~/pub/first).  This directory contains a contact file that lists the>current members and their constituencies and contact information>(filename "first-contacts").>While CERT is a great organization, other response teams who do handle>incidents on their parts of the Internet merit some mention as well ->perhaps mentioning the existence of this file would help to do that in a>limited space.The file mentioned is a comprehensive listing of contact points pernetwork for security incidents.  It is too large to reproduce here, Isuggest that the reader obtains a copy for his/her self by the meansgiven.Q.10 What is a firewall?A (Internet) firewall is a machine which is attached (usually) betweenyour site and a wide area network.  It provides controllable filteringof network traffic, allowing restricted access to certain internet portnumbers (ie: services that your machine would otherwise provide to thenetwork as a whole) and blocks access to pretty well everything else.Similar machines are available for other network types, too.Firewalls are an effective "all-or-nothing" approach to dealing withexternal access security, and they are becoming very popular, with therise in Internet connectivity.For more information on these sort of topics, see the Gateway paper by[Cheswick], below.Q.11 Why shouldn't I use setuid shell scripts?You shouldn't use them for a variety of reasons, mostly involving bugsin the Unix kernel.  Here are a few of the more well known problems,some of which are fixed on more recent operating systems.1) If the script begins "#!/bin/sh" and a link (symbolic or otherwise)can be made to it with the name "-i", a setuid shell can be immediatelyobtained because the script will be invoked: "#!/bin/sh -i", ie: aninteractive shell.2) Many kernels suffer from a race condition which can allow you toexchange the shellscript for another executable of your choice betweenthe times that the newly exec()ed process goes setuid, and when thecommand interpreter gets started up.  If you are persistent enough, intheory you could get the kernel to run any program you want.3) The IFS bug: the IFS shell variable contains a list of characters tobe treated like whitespace by a shell when parsing command names.  Bychanging the IFS variable to contain the "/" character, the command"/bin/true" becomes "bin true".All you need do is export the modified IFS variable, install a commandcalled "bin" in your path, and run a setuid script which calls"/bin/true".  Then "bin" will be executed whilst setuid.If you really must write scripts to be setuid, either  a) Put a setuid wrapper in "C" around the script, being very careful  to reset IFS and PATH to something sensible before exec()ing the  script.  If your system has runtime linked libraries, consider the  values of the LD_LIBRARY_PATH also.  b) Use a scripting language like Perl which has a safe setuid  facility, and is proactively rabid about security.