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CERT Advisory 093
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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)
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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
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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
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* 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
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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
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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
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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
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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.
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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.
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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
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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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