INFORMATION BULLETIN INFORMATION BULLETIN April 28, 2000 17:00 GMT
PROBLEM: There are continuing compromises of machines running the Domain
Name System (DNS) server software that is part of BIND
("named"), including compromises of machines that are not being
used as DNS Servers.
PLATFORM: Systems running various vulnerable versions of BIND (including
on machines where the system administrator does not realize a
DNS server is running).
DAMAGE: Allows intruder to gain root access.
SOLUTION: Upgrade the vulnerable systems with their associated DNS
security patches and workarounds.
VULNERABILITY The risk is HIGH. The exploits have appeared in public forums.
ASSESSMENT:
[ Start CERT/CC Advisory ]
CERT(r) Advisory CA-2000-03 Continuing Compromises of DNS servers
Original release date: April 26, 2000
Last revised: April 26, 2000
Source: CERT/CC
Systems Affected
* Systems running various vulnerable versions of BIND (including on
machines where the system administrator does not realize a DNS
server is running)
Overview
This CERT Advisory addresses continuing compromises of machines
running the Domain Name System (DNS) server software that is part of
BIND ("named"), including compromises of machines that are not being
used as DNS Servers. The Advisory also reports that a significant
number of delegated(*) DNS servers in the in-addr.arpa tree are running
outdated versions of DNS software, and urges system and network
administrators to ensure that they are up-to-date with DNS security
patches and workarounds.
______________________________________________________________________
The CERT Coordination Center has received reports of continuing
activity indicating that intruders are targeting machines running
vulnerable versions of "named" . We continue to receive regular, daily
reports that sites running unpatched, vulnerable versions of "named"
have been compromised. CERT Advisory CA-99-14 "Multiple
Vulnerabilities in BIND" describes the BIND NXT record privileged
compromise vulnerability that is being exploited. We encourage you to
review this advisory and to apply the appropriate patches if you have
not done so already. The advisory is available at
http://www.cert.org/advisories/CA-99-14-bind.html
Some sites with compromised systems have found one of the following
empty directories on systems where the NXT record vulnerability was
successfully exploited:
/var/named/ADMROCKS
/var/named/O
Other artifacts that are commonly found include
* inetd started with an intruder-supplied configuration file in /tmp
that provides a backdoor into the system
* modified /etc/inittab and/or system startup files to load intruder
processes at boot time
* Trojan horse versions of sshd and /bin/login designed to provide a
backdoor into a compromised system
* complete rootkits that include Trojan horse replacements for
system binaries, sniffers, denial-of-service tools, vulnerability
scanners, exploits, etc.
* newer versions of BIND
Compromised systems are commonly used to search for and attack other
potentially vulnerable systems.
In many of the reports of DNS server compromises, compromised machines
running DNS server software were not being used as DNS servers. The
DNS server software was running because it was installed by default
(unknowingly in many cases) when the machines were configured. This
software was not up to date with security patches and workarounds; and
since the system administrators were not planning to have the machines
operate as DNS servers, they did not ensure the software was up to
date, or simply disable the DNS server software on the machine. We
encourage system and network administrators to disable DNS server
software, and other services, on machines where the services are not
needed.
We have also received information from Bill Manning of the USC/ISI
concerning DNS servers running vulnerable versions of domain name
server software. Since 1997, Bill Manning sweeps the inverse tree
(in-addr.arpa) on a quarterly basis to verify the accuracy of
delegations within that hierarchy. Using the first quarter survey
results, he compiled a list of what version of DNS server software
the servers were running. Of the responding DNS servers that are
delegated(*) DNS servers for the in-addr.arpa zone, more than 50%
of these DNS servers were running older, vulnerable versions of
BIND (any vulnerabilities, not just the NXT vulnerability). This is
significant because the compromise of DNS servers that are
delegated DNS servers can have impact on the security of other
organizations in addition to the organization operating the DNS
server.
A copy of the survey results are available at
http://www.isi.edu/~bmanning/in-addr-audit.html
Based on the number of older versions being run, and the rate of
compromises, we believe the number of DNS servers running older,
vulnerable versions of BIND have not significantly decreased since the
survey was published.
We encourage DNS server operators to ensure that their DNS server
software is up to date with the most recent versions of the DNS server
software and that all security patches and workarounds have been
applied.
delegated DNS server: a delegated DNS is a DNS server that is assigned
responsibility for responding to requests for a portion of the DNS
hierarchy. For more information on delegation, see the section on
delegation in DNS and BIND third edition, by Paul Albitz and Cricket
Liu, O'Reilly and Associates, 1998.
Advisory Author: Jeffrey J. Carpenter
_________________________________________________________________
The CERT Coordination Center thanks Bill Manning, USC/ISI, for
providing information used in this CERT Advisory.
______________________________________________________________________
This document is available from:
http://www.cert.org/advisories/CA-2000-03.html
______________________________________________________________________
CERT/CC Contact Information
Email: cert@cert.org
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
U.S.A.
CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4)
Monday through Friday; they are on call for emergencies during other
hours, on U.S. holidays, and on weekends.
Using encryption
We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
http://www.cert.org/CERT_PGP.key
If you prefer to use DES, please call the CERT hotline for more
information.
Getting security information
CERT publications and other security information are available from
our web site
http://www.cert.org/
To be added to our mailing list for advisories and bulletins, send
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Patent and Trademark Office.
______________________________________________________________________
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Engineering Institute is furnished on an "as is" basis. Carnegie
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does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
Copyright 2000 Carnegie Mellon University.
[ End CERT/CC Advisory ]
CIAC wishes to acknowledge the contributions of CERT/CC for the information contained in this bulletin.
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