============================================================================= CA-95:06 CERT Advisory April 3, 1995 Security Administrator Tool for Analyzing Networks (SATAN) ----------------------------------------------------------------------------- The CERT Coordination Center staff has examined beta version 0.51 of the Security Administrator Tool for Analyzing Networks (SATAN). This advisory contains information based on our review of this pre-release version. When the official release is available, we will distribute an updated advisory. SATAN is scheduled for release on April 5, 1995, at 14:00 GMT. 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. 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/tech_tips/security_info ftp://info.cert.org/tech_tips/anonymous_ftp ftp://info.cert.org/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 and CA-94:15.README 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-94:02.README CA-93:15.SunOS.and.Solaris.vulnerabilities CA-92:15.Multiple.SunOS.vulnerabilities.patches CA-92:12.REVISED.SunOS.rpc.mountd.vulnerability 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 and CA-95:05.README 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. 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/anonymous_ftp 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 11. wu-ftpd vulnerability See CA-93:06, CA-94:07, and CA-94:07.README for more information about ftpd. 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 and CA-93:14.README contain 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. 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. 8. Getting more information about SATAN --------------------------------------- As noted above, SATAN documentation is available from ftp://ftp.win.tue.nl/pub/security/satan_doc.tar.Z Additional documents are available through a mail server set up by one of the authors. Send mail to majordomo@wzv.win.tue.nl Put the following text in the body (not subject): get satan mirror-sites get satan release-plan get satan description get satan admin-guide-to-cracking.101 The last document contains "Improving the Security of Your Site by Breaking Into It," 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 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.