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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


Recent Activity

   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
       and NetBus.

       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
       vulnerabilities including

       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
       available at

       What's New and Updated Since the last CERT Summary, we have
       developed new and updated

          + Incident Notes
          + Vulnerability Notes
          + Advisories
          + 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

        Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
                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

       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 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
       To be added to our mailing list for advisories and bulletins, send
       email to This email address is being protected from spambots. You need JavaScript enabled to view it. and include SUBSCRIBE
       your-email-address in the subject of your message.

       Copyright 1998 Carnegie Mellon University.

       Conditions for use, disclaimers, and sponsorship information can
       be found in

       * CERT is registered in the U.S. Patent and Trademark Office

       Any material furnished by Carnegie Mellon University and the
       Software Engineering Institute is furnished on an "as is" basis.
       Carnegie Mellon University makes no warranties of any kind, either
       expressed or implied as to any matter including, but not limited
       to, warranty of fitness for a particular purpose or
       merchantability, exclusivity or results obtained from use of the
       material. Carnegie Mellon University does not make any warranty of
       any kind with respect to freedom from patent, trademark, or
       copyright infringement.

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