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CA-92:03                        CERT Advisory
 			      February 17, 1992
                          Internet Intruder Activity

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The Computer Emergency Response Team/Coordination Center (CERT/CC) has
received information regarding a significant intrusion incident on the
Internet.  Systems administrators should be aware that many systems on
the Internet have been compromised due to this activity.  To identify
whether your systems have been affected by the activity we recommend
that all system administrators check for the signs of intrusion
detailed in this advisory.

This advisory describes the activities that have been identified as
part of this particular incident.  This does not address the
possibility that systems may have been compromised due to other,
unrelated intrusion activity.

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I.   Description

     The intruders gained initial access to a host by discovering a
     password for a user account on the system.  They then attempted
     to become root on the compromised system.

II.  Impact
	
     Having gained root access on a system, the intruders installed
     trojan binaries that captured account information for both
     local and remote systems.  They also installed set-uid root
     shells to be used for easy root access.

III. Solution 

     A. Check your systems for signs of intrusion due to this incident.

        1. Check the su, ftpd, and ftp binaries (for example, "/bin/su",
           "/usr/ucb/ftp" and "/usr/etc/in.ftpd" on Sun systems)
           against copies from distribution media.

        2. Check for the presence of any of the following files:
           "/usr/etc/..." (dot dot dot), "/var/crash/..." (dot dot dot), 
           "/usr/etc/.getwd", "/var/crash/.getwd", or 
           "/usr/kvm/..." (dot dot dot).

        3. Check for the presence of "+" in the "/etc/hosts.equiv" file.

        4. Check the home directory for each entry in the "/etc/passwd"
           file for the presence of a ".rhosts" file containing
           "+ +" (plus space plus).

        5. Search the system for the presence of the following set-uid
           root files: "wtrunc" and ".a".

        6. Check for the presence of the set-uid root file "/usr/lib/lpx".


     B. Take the following steps to secure your systems.

        1. Save copies of the identified files to removable media.

        2. Replace any modified binaries with copies from
           distribution media.

        3. Remove the "+" entry from the "/etc/hosts.equiv" file and 
           the "+ +" (plus space plus) entry from any ".rhosts" files.

        4. Remove any of the set-uid root files that you find, which are
           mentioned in A5 or A6 above.
           
        5. Change every password on the system.

	6. Inspect the files mentioned in A2 above for references
           to other hosts.

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If you believe that your system has been compromised, contact CERT/CC or
your representative in FIRST (Forum of Incident Response and Security Teams).

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 (24-hour hotline)
           CERT/CC personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4),
           on call for emergencies during other hours.

Computer Emergency Response Team/Coordination Center (CERT/CC)
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

Past advisories, information about FIRST representatives, and other
information related to computer security are available for anonymous ftp
from cert.org (192.88.209.5).

