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CERT(sm) Advisory CA-95:06
Original issue date:  April 3, 1995
Last revised: August 30, 1996
              Information previously in the README was inserted
              into the advisory. Updated tech tip references.

              A complete revision history is at the end of this file.

Topic: Security Administrator Tool for Analyzing Networks (SATAN)
- -----------------------------------------------------------------------------

The CERT Coordination Center staff examined beta version 0.51 of the Security
Administrator Tool for Analyzing Networks (SATAN). This advisory initially
contained information based on our review of this pre-release version. When
the official release became available, we updated the advisory based on version
1.1.1.

1. What is SATAN?
- ------------------
SATAN is a testing and reporting tool that collects a variety of information
about networked hosts. The currently available documentation can be found at
         ftp://ftp.win.tue.nl/pub/security/satan_doc.tar.Z

SATAN gathers information about specified hosts and networks by examining
network services (for example, finger, NFS, NIS, ftp, and rexd).  It can then
report this data in a summary format or, with a simple rule-based system,
investigate potential security problems. Problems are described briefly and
pointers provided to patches or workarounds. In addition to reporting
vulnerabilities, SATAN gathers general network information (network topology,
network services run, types of hardware and software being used on the
network).  As described in the SATAN documentation, SATAN has an exploratory
mode that allows it to probe hosts that have not been explicitly specified.
Thus, SATAN could probe not only targeted hosts, but also hosts outside your
administrative domain.

Section 4 below lists the vulnerabilities currently probed by SATAN.

After the release of SATAN 1.0, we published a separate advisory describing a
vulnerability in SATAN. If you do not already have a copy of CA-95:07a, we
strongly urge you to obtain a copy from

      ftp://info.cert.org/pub/cert_advisories/CA-95:07a.REVISED.satan.vul

As we receive new information about SATAN, we will update advisories
CA-95:06 (SATAN in general) and CA-95:07a (vulnerability in SATAN).
We encourage you to check our advisories regularly for updates to relating to
your site.

2. Potential Impact of SATAN
- ----------------------------
SATAN was designed as a security tool for system and network administrators.
However, given its wide distribution, ease of use, and ability to scan remote
networks, SATAN is also likely to be used to locate vulnerable hosts for
malicious reasons. It is also possible that sites running SATAN for a
legitimate purpose will accidentally scan your system via SATAN's exploratory
mode.

Although the vulnerabilities SATAN identifies are not new, the ability to
locate them with a widely available, easy-to-use tool increases the level of
threat to sites that have not taken steps to address those vulnerabilities. In
addition, SATAN is easily extensible. After it is released, modified versions
might scan for other vulnerabilities as well and might include code to
compromise systems. 


3. How to Prepare for the Release of SATAN
- ------------------------------------------

* Examine your systems for the vulnerabilities described below and implement
  security fixes accordingly.

* In addition to reading the advisories cited for specific vulnerabilities
  below, consult the following documents for guidance on improving the
  security of your systems:
 
     ftp://info.cert.org/pub/tech_tips/intruder_detection_checklist
     ftp://info.cert.org/pub/tech_tips/UNIX_configuration_guidelines
     ftp://info.cert.org/pub/tech_tips/anonymous_ftp_config
     ftp://info.cert.org/pub/tech_tips/packet_filtering

* Contact your vendor for information on available security patches, and
  ensure that all patches have been installed at your site.

* Use the tools listed in Section 5 to assist you in assessing and improving
  the security of your systems.


4. Vulnerabilities Probed by SATAN
- ----------------------------------
Listed below are vulnerabilities that beta version 0.51 of SATAN tests for,
along with references to CERT advisories and other documents where applicable.

Administrators should verify the state of their systems and perform corrective
actions as necessary. We cannot stress enough the importance of good network
configuration and the need to install all available patches.

   1. NFS export to unprivileged programs
   2. NFS export via portmapper
   3. Unrestricted NFS export

      See CERT advisory CA-94:15 for security measures you can take to address
      NFS vulnerabilities. 

      The following advisories also address problems related to NFS:
             CA-94:02.REVISED.SunOS.rpc.mountd.vulnerability
             CA-93:15.SunOS.and.Solaris.vulnerabilities
             CA-92:15.Multiple.SunOS.vulnerabilities.patches
             CA-91:21.SunOS.NFS.Jumbo.and.fsirand

   4. NIS password file access
      See CERT advisory CA-92:13 for information about SunOS 4.x machines using
      NIS, and CA-93:01 for information about HP machines.

   5. rexd access
      We recommend filtering the rexd service at your firewall and commenting
      out rexd in the file /etc/inetd.conf. 
      
      See CERT advisory CA-92:05 for more information about IBM AIX machines
      using rexd, and CA-91:06 for information about NeXT.
   
   6. Sendmail vulnerabilities
      See CERT advisory CA-95:05 for the latest information we have published
      about sendmail.  

   7. TFTP file access
      See CERT advisory CA-91:18 for security measures that address TFTP access
      problems. In addition, CA-91:19 contains information for IBM AIX users.

   8. Remote shell access
      We recommend that you comment out rshd in the file /etc/inetd.conf or
      protect it with a TCP wrapper. A TCP/IP wrapper program is available from
           ftp://info.cert.org/pub/tools/tcp_wrappers/

   9. Unrestricted X server access
      We recommend filtering X at your firewall. Additional advice about
      packet filtering is available by anonymous FTP from
             ftp://info.cert.org/pub/tech_tips/packet_filtering

   10. Writable FTP home directory
       See CERT advisory CA-93:10. 
       Guidance on anonymous FTP configuration is also available from
             ftp://info.cert.org/pub/tech_tips/anonymous_ftp_config

   11. wu-ftpd vulnerability
       See CA-93:06 and CA-94:07 for more information about ftpd.

   12. Unrestricted dial-out modem available via TCP.
       Place modems behind a firewall or put password or other extra
       authentication on them (such as S/Key or one-time passwords).
       For information on one-time passwords, see CERT advisory CA-94:01,
       Appendix B.

Note: In addition to our FTP archive at info.cert.org, CERT documents are
      available from the following sites, and others which you can locate
      by using archie:

          ftp://coast.cs.purdue.edu/pub/mirrors/cert.org/cert_advisories 
          ftp://unix.hensa.ac.uk/pub/uunet/doc/security/cert_advisories
          ftp://ftp.luth.se/pub/misc/cert/cert_advisories
          ftp://ftp.switch.ch/network/security/cert_advisories
          ftp://corton.inria.fr/CERT/cert_advisories
          ftp://ftp.inria.fr/network/cert_advisories
          ftp://nic.nordu.net/networking/security/cert_advisories

5. Currently Available Tools
- -----------------------------
The following tools are freely available now and can help you improve your
site's security before SATAN is released.

COPS and ISS can be used to check for vulnerabilities and configuration
weaknesses. 

     COPS is available from ftp//info.cert.org:/pub/tools/cops/*

     ISS is available from
     ftp://ftp.uu.net/usenet/comp.sources.misc/volume39/iss  
     CERT advisory CA-93:14 contains information about ISS.

TCP wrappers can provide access control and flexible logging to most network
services. These features can help you prevent and detect network attacks. This
software is available by anonymous FTP from

          ftp://info.cert.org/pub/tools/tcp_wrappers/*

The TAMU security package includes tools to check for vulnerabilities and
system configuration weaknesses, and it provides logging and filtering of
network services. This software is available by anonymous FTP from

          ftp://net.tamu.edu/pub/security/TAMU/*

The Swatch log file monitor allows you to identify patterns in log file entries
and associate them with actions. This tool is available from

          ftp://ee.stanford.edu/pub/sources/swatch.tar.Z


6. Detecting Probes
- -------------------
One indication of attacks by SATAN, and other tools, is evidence of a heavy
scan of a range of ports and services in a relatively short time.  Many UNIX
network daemons do not provide sufficient logging to determine if SATAN is
probing the system. TCP wrappers, the TAMU tools, and Swatch can provide the
logging you need.

New tools are becoming available on the network to help you detect
probes, but the CERT staff has not evaluated them.

Although detection tools can be helpful, keep in mind that their
effectiveness depends on the nature and availability of your logs and
that the tools may become less effective as SATAN is modified. The
most important thing you can do is take preventive action to secure
your systems.

7. Using SATAN
- ---------------
Running SATAN on your systems will provide you with the same information an
attacker would obtain, allowing you to correct vulnerabilities. If you choose
to run SATAN, we urge you to read the documentation carefully. Also,
note the following:

* It is easy to accidentally probe systems you did not intend to. If this
  occurs, the probed site may view the probe(s) as an attack on their
  system(s).

* Take special care in setting up your configuration file, and in selecting the
  probe level when you run SATAN. 

* Explicitly bound the scope of your probes when you run SATAN. Under "SATAN
  Configuration Management," explicitly limit probes to specific hosts and
  exclude specific hosts.  

* When you run SATAN, ensure that other users do not have read access to your
  SATAN directory.

* In some cases, SATAN points to CERT advisories. If the link does not work
  for you, try getting the advisories by anonymous FTP.

* Install all relevant security patches for the system on which you will
  run SATAN.

* Ensure that the SATAN directory tree cannot be read by users other
  than root.

* Execute SATAN only from the console of the system on which it is
  installed (e.g., do not run SATAN from an X terminal, from a diskless
  workstation, or from a remote host).

* Ensure that the SATAN directory tree is not NFS-mounted from a remote
  system.

* It is best to run SATAN from a system that does not support multiple
  users.

8. Getting more information about SATAN
- ---------------------------------------

The SATAN authors report that SATAN 1.1.1 is available from many
sites, including:

     ftp://ftp.win.tue.nl/pub/security/satan-1.1.1.tar.Z
     ftp://ftp.win.tue.nl/pub/security/satan-1.1.1.README
     ftp://ftp.win.tue.nl/pub/security/satan_doc.tar.Z
     ftp://ftp.win.tue.nl/pub/security/satan_doc.README

To get a current list of sites, send mail to:

     majordomo@wzv.win.tue.nl

and put in the body of your message

     get satan mirror-sites

You can also use archie to locate sites that have SATAN.

MD5 checksums for SATAN:

     satan-1.1.1.README = 3f935e595ab85ee28b327237f1d55287
     satan-1.1.1.tar.Z = de2d3d38196ba6638b5d7f37ca8c54d7
     satan-1.1.1.tar.Z.asc = a9261070885560ec11e6cc1fe0622243
     satan_doc.README = 4ebe05abc3268493cdea0da786bc9589
     satan_doc.tar.Z = 951d8bfca033eeb483a004a4f801f99a
     satan_doc.tar.Z.asc = 3216053386f72347956f2f91d6c1cb7c

Also available is "Improving the Security of Your Site by Breaking
Into It" (admin-guide-to-cracking.101), a 1993 paper in which the authors give
their rationale for creating SATAN.

- ---------------------------------------------------------------------------
The CERT Coordination Center staff thanks Dan Farmer and Wieste Venema for the
the opportunity to examine pre-release versions of SATAN. We also appreciate
the interaction with the response teams at AUSCERT, CIAC, and DFN-CERT, and
feedback from Eric Allman.
- ---------------------------------------------------------------------------

If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident
Response and Security Teams (FIRST).

If you wish to send sensitive incident or vulnerability information to
CERT staff by electronic mail, we strongly advise that the e-mail be
encrypted.  The CERT Coordination Center can support a shared DES key, PGP
(public key available via anonymous FTP on info.cert.org), or PEM (contact
CERT staff for details).

Internet E-mail: cert@cert.org
Telephone: +1 412-268-7090 (24-hour hotline)
           CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),
           and are on call for emergencies during other hours.
Fax: +1 412-268-6989

Postal address:  CERT Coordination Center
                 Software Engineering Institute
                 Carnegie Mellon University
                 Pittsburgh, PA 15213-3890
                 USA

CERT advisories and bulletins are posted on the USENET newsgroup
comp.security.announce. If you would like to have future advisories and
bulletins mailed to you or to a mail exploder at your site, please send mail
to cert-advisory-request@cert.org.

Past advisories, CERT bulletins, information about FIRST representatives, and
other information related to computer security are available for anonymous 
FTP from info.cert.org. 



Copyright 1995, 1996 Carnegie Mellon University
This material may be reproduced and distributed without permission provided it
is used for noncommercial purposes and the copyright statement is included.

CERT is a service mark of Carnegie Mellon University.

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UPDATES

Note to users of LINUX SATAN: There was a posting to USENET that a
Trojan horse was introduced into a version of LINUX SATAN binaries
archived on ftp.epinet.com.  CERT staff have not verified that this
Trojan horse exists; however, if you are using LINUX SATAN and
believe your version may be compromised, we suggest you obtain
additional information from

        ftp://ftp.epinet.com/pub/linux/security

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Revision history

Aug. 30, 1996  Information previously in the README was inserted
               into the advisory. Updated tech tip references.

Apr. 11, 1995  Updated information based on SATAN 1.1.1 (original advisory
               was based on beta version 0.51):
                 Introduction - added reference to CA-95:07a
                 Sec. 4 - added information on SATAN probe for unrestricted
                          modems 
                 Sec. 6 - added a note on tools for detecting probes
                 Sec. 7 - added five additional precautions
                 Sec. 8 - where to get a copy of SATAN 
                          checksums for SATAN and documentation 
                          where to send comments about SATAN 

Apr. 11, 1995  Sec. 3 - pathnames corrected in Sec. 3
               Sec. 4-5 - colons noted in (and subsequently removed from) URLs
          
Apr. 11, 1995  Updates section - added a note on LINUX SATAN





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