Date: 15 December 1998
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AUSCERT External Security Bulletin Redistribution
ESB-98.189 -- CERT Summary CS-98.08
15 December 1998
The CERT Coordination Centre has released the following advisory concerning
recent intruder activity. Reports to AusCERT indicate that similar
activity is evident in Australia and New Zealand.
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CERT Summary CS-98.08
December 14, 1998
The CERT Coordination Center periodically issues the CERT Summary to
draw attention to the types of attacks currently being reported to our
incident response team, as well as to other noteworthy incident and
vulnerability information. The summary includes pointers to sources of
information for dealing with the problems.
Past CERT Summaries are available from
Since the last CERT Summary, issued in August 1998 (CS-98.07), we have
seen these trends in incidents reported to us.
1. Vulnerability in mountd
We have seen many reports of this vulnerability being exploited on
NFS servers running certain implementations of mountd, primarily
Linux. On some systems, the vulnerable NFS server is enabled by
default. This vulnerability can be exploited even if the NFS
server does not export any file systems. Intruders who are able to
exploit the vulnerability can do it remotely and can gain
administrative access. We encourage you to review CERT Advisory
CA-98.12, which describes the mountd vulnerability in more detail.
The advisory is available from
2. Spread of Windows-Based Trojan Horse Programs
In recent months, we have seen the spread of Windows-based Trojan
horse programs. The most frequently reported incidents involving
Windows-based Trojan horse programs involve the tools Back Orifice
We receive occasional reports of compromised machines that have
one of these tools installed; however, the majority of reports
involving these tools are from sites noticing intruders scanning
their networks for the presence of these tools. We receive daily
reports indicating that intruders are actively scanning networks
to find running instances of these tools on already compromised
Look for the following symptoms to detect those scans:
NetBus - connection request (SYN) packets to TCP port 12345
Back Orifice - UDP packets to port 31337
Keep in mind that these tools can be configured to listen on
different ports. Because of this, we encourage you to investigate
any unexplained network traffic.
Because these tools are Trojan horses, users must install them or
be tricked into installing them. To impede the proliferation of
this class of tools, we encourage system administrators to educate
their users about safe computing practices (e.g., only install
software from trusted sources, and use virus scanning software on
any newly introduced software).
For more information about Back Orifice, we encourage you to
review CERT Vulnerability Note VN-98.07.
3. Widespread Scans
We continue to receive numerous daily reports of intruders using
tools to scan networks for multiple vulnerabilities. On July 2, we
published an incident note detailing this activity. This document
is available at
Since July 2 these tools have become a bit more sophisticated.
Variants of the "mscan" tool now probe for the most recent
Additionally, these tools incorporate the ability to identify a
machine's architecture and operating system.
4. Scripted Tools
Very recently, we have received a few reports indicating that
intruders are executing widespread attacks using scripted tools to
control various information-gathering and exploitation tools. The
combination of functionality used by the scripted tools enables
intruders to automate the process of identifying and exploiting
known vulnerabilities in specific host platforms. This information
is available at
5. Stealth Scanning Techniques
We have received a few reports indicating that intruders are using
stealth scanning techniques. Stealth scanning is used by intruders
to avoid detection. Details about stealth scanning techniques are
What's New and Updated Since the last CERT Summary, we have
developed new and updated
+ Incident Notes
+ Vulnerability Notes
+ Vendor-Initated Bulletins
+ System Survivability Research information
+ Incident Response Courses
If you are interested in any of these, please see our What's New
web page for descriptions and links:
CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
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.
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.
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Copyright 1998 Carnegie Mellon University.
Conditions for use, disclaimers, and sponsorship information can
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Carnegie Mellon University makes no warranties of any kind, either
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This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to use any or all of this information is
the responsibility of each user or organisation, and should be done so in
accordance with site policies and procedures.
NOTE: This is only the original release of the security bulletin. It will
not be updated when updates to the original are made. If downloading at
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Contact information for the authors of the original document is included
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information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
If you believe that your system has been compromised, contact AusCERT or
your representative in FIRST (Forum of Incident Response and Security
Internet Email: email@example.com
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for emergencies.
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