<H4>This advisory is being published jointly by the CERT Coordination Center and the Federal Computer Incident Response Capability (FedCIRC).</H4> <p>Original release date: January 3, 2000<BR> Source: CERT/CC and FedCIRC<BR> <P>A complete revision history is at the end of this file. <H3>Systems Affected</H3> <UL> <LI>All systems connected to the Internet can be affected by denial-of-service attacks. </UL> <H2>I. Description</H2> <H4>Continued Reports of Denial-of-Service Problems</H4> <P>We continue to receive reports of new developments in denial-of-service tools. This advisory provides pointers to documents discussing some of the more recent attacks and methods to detect some of the tools currently in use. Many of the denial-of-service tools currently in use depend on the ability of an intruder to compromise systems first. That is, intruders exploit known vulnerabilities to gain access to systems, which they then use to launch further attacks. For information on how to protect your systems, see the <A HREF="#solutions">solution section</a> below. <P>Security is a <A HREF="#commeff">community effort</a> that requires diligence and cooperation from all sites on the Internet. <H4>Recent Denial-of-Service Tools and Developments</H4> <p>One recent report can be found in <A HREF="http://www.cert.org/advisories/CA-99-17-denial-of-service-tools.html">CERT Advisory CA-99-17</a>. <p>A distributed denial-of-service tool called "Stacheldraht" has been discovered on multiple compromised hosts at several organizations. In addition, one organization reported what appears to be more than 100 different connections to various Stacheldraht agents. At the present time, we have not been able to confirm that these are connections to Stacheldraht agents, though they are consistent with an analysis provided by Dave Dittrich of the University of Washington, available at <DL><DD> <A HREF="http://staff.washington.edu/dittrich/misc/stacheldraht.analysis"> http://staff.washington.edu/dittrich/misc/stacheldraht.analysis</A> </DL> <p>Also, Randy Marchany of Virginia Tech released an <A HREF="http://www.sans.org/y2k/TFN_toolkit.htm">analysis</A> of a TFN-like toolkit, available at <DL><DD> <A HREF="http://www.sans.org/y2k/TFN_toolkit.htm"> http://www.sans.org/y2k/TFN_toolkit.htm</A> </DL> <p> The ISS X-Force Security Research Team published information about trin00 and TFN in their <A HREF="http://xforce.iss.net/alerts/advise40.php3">December 7 Advisory</a>, available at <DL> <DD> <A HREF="http://xforce.iss.net/alerts/advise40.php3">http://xforce.iss.net/alerts/advise40.php3</a> </DL> <P>A general discussion of denial-of-service attacks can be found in a <A HREF="http://www.cert.org/tech_tips/denial_of_service.html">CERT/CC Tech Tip</A> available at <DL> <DD> <A HREF="http://www.cert.org/tech_tips/denial_of_service.html"> http://www.cert.org/tech_tips/denial_of_service.html</A> </DL> <H2>II. Impact</H2> <P>Denial-of-service attacks can severely limit the ability of an organization to conduct normal business on the Internet. <A NAME="solutions"> <H2>III. Solution</H2> <P>Solutions to this problem fall into a variety of categories. <H4>Awareness</H4> <P>We urge all sites on the Internet to be aware of the problems presented by denial-of-service attacks. In particular, keep the following points in mind: <UL> <A NAME="commeff"> <LI><P>Security on the Internet is a community effort. Your security depends on the overall security of the Internet in general. Likewise, your security (or lack thereof) can cause serious harm to others, even if intruders do no direct harm to your organization. Similarly, machines that are not part of centralized computing facilities and that may be managed by novice or part-time system administrators or may be unmanaged, can be used by intruders to inflict harm on others, even if those systems have no strategic value to your organization. <P><LI>Systems used by intruders to execute denial-of-service attacks are often compromised via well-known vulnerabilities. Keep up-to-date with patches and workarounds on all systems. <P><LI>Intruders often use source-address spoofing to conceal their location when executing denial-of-service attacks. We urge all sites to implement ingress filtering to reduce source address spoofing on as many routers as possible. For more information, see <A HREF="http://info.internet.isi.edu:80/in-notes/rfc/files/rfc2267.txt">RFC2267</a>. <P><LI>Because your security is dependent on the overall security of the Internet, we urge you to consider the effects of an extended network or system outage and make appropriate contingency plans where possible. <P><LI>Responding to a denial-of-service attack may require the cooperation of multiple parties. We urge all sites to develop the relationships and capabilities described in the results of our recent workshop <i>before</i> you are a victim of a distributed denial-of-service attack. This document is available at <P> <DL><DD> <A HREF="http://www.cert.org/reports/dsit_workshop.pdf"> http://www.cert.org/reports/dsit_workshop.pdf</A> </DL> </UL> <H4>Detection</H4> <P>A variety of tools are available to detect, eliminate, and analyze distributed denial-of-service tools that may be installed on your network. <P>The <A HREF="http://www.nipc.gov">National Infrastructure Protection Center</a> has recently announced a tool to detect trin00 and TFN on some systems. For more information, see <DL><DD> <A HREF="http://www.nipc.gov/warnings/alerts/1999/trinoo.htm"> http://www.nipc.gov/warnings/alerts/1999/trinoo.htm</A> </DL> <p>Part of the <A HREF="http://staff.washington.edu/dittrich/misc/stacheldraht.analysis">analysis</a> done by Dave Dittrich includes a Perl script named <i>gag</i> which can be used to detect stacheldraht agents running on your local network. See Appendix A of that analysis for more information. <p><A HREF="http://www.iss.net">Internet Security Systems</a> released updates to some of their tools to aid sites in detecting trin00 and TFN. For more information, see <dl><dd> <A HREF="http://www.iss.net/cgi-bin/dbt-display.exe/db_data/press_rel/release/122899199.plt"> http://www.iss.net/cgi-bin/dbt-display.exe/db_data/press_rel/release/122899199.plt</a> </dl> <H4>Prevention</H4> <P>We urge all sites to follow sound security practices on all Internet-connected systems. For helpful information, please see <DL><DD> <A HREF="http://www.cert.org/tech_tips/">http://www.cert.org/tech_tips</a> <dd> <A HREF="http://www.sans.org">http://www.sans.org</a> </DL> <H4>Response</H4> <P>For information on responding to intrusions when they do occur, please see <dl><dd> <A HREF="http://www.cert.org/nav/recovering.html">http://www.cert.org/nav/recovering.html</a> <dd> <a HREF="http://www.sans.org/newlook/publications/incident_handling.htm"> http://www.sans.org/newlook/publications/incident_handling.htm</a> <dd> </dl> <P>The United States <A HREF="http://www.fbi.gov">Federal Bureau of Investigation</a> is conducting criminal investigations involving TFN where systems appears to have been compromised. U.S. recipients are encouraged to contact <A HREF="http://www.fbi.gov/contact/fo/fo.htm">their local FBI Office</a>. <HR NOSHADE> <P>We thank Dave Dittrich of the <A HREF="http://washington.edu">University of Washington</a>, Randy Marchany of <a href="http://www.vt.edu">Virginia Tech</a>, <A HREF="http://www.iss.net">Internet Security systems</a>, <A HREF="http://www.uu.net">UUNet</a>, the <A HREF="http://www.y2k.gov"</a>Y2K-ICC</a>, the <A HREF="http://www.nipc.gov">National Infrastructure Protection Center</a>, Alan Paller and Steve Northcutt of <A HREF="http://www.sans.org">The SANS Institute</a>, <A HREF="http://www.mitre.org">The MITRE Corporation</a>, Jeff Schiller of <A HREF="http://www.mit.edu">The Massachusetts Institute of Technology</a>, Jim Ellis of <A HREF="http://www.sun.com">Sun Microsystems</a>, Vern Paxson of <A HREF="http://www.lbl.gov">Lawrence Berkeley National Lab</a>, and Richard Forno of <A HREF="http://www.networksolutions.com">Network Solutions</a>. <p><!--#include virtual="/include/footer_nocopyright.html" --> </p> <p>Copyright 2000 Carnegie Mellon University.</p> <HR> Revision History <PRE> </PRE> |