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                     National Cyber Alert System

               Technical Cyber Security Alert TA07-059A


Sun Solaris Telnet Worm

   Original release date: February 28, 2007
   Last revised: --
   Source: US-CERT


Systems Affected

     * Sun Solaris 10 (SunOS 5.10)
     * Sun "Nevada" (SunOS 5.11)

   Both SPARC and Intel (x86) architectures are affected.


Overview

   A worm is exploiting a vulnerability (VU#881872) in the Sun Solaris
   telnet daemon (in.telnetd).


I. Description

   A worm is exploiting a vulnerability in the telnet daemon
   (in.telnetd) on unpatched Sun Solaris systems. The vulnerability
   allows the worm (or any attacker) to log in via telnet (23/tcp)
   with elevated privileges. Further details about the vulnerability
   are available in Vulnerability Note VU#881872 (CVE-2007-0882).

   Because VU#881872 is trivial to exploit and sufficient technical
   detail is publicly available, any attacker, not just this worm,
   could exploit vulnerable systems.

   Characteristics of the worm include, but are not limited to:
   
     * Exploiting VU#881872 to log in via telnet as the users adm or lp
     * Changing permissions on /var/adm/wtmpx to -rw-r--rw-
     * Creating the directory .adm in /var/adm/sa/
     * Adding .profile files to /var/adm/ and /var/spool/lp/
     * Installing an authenticated backdoor shell on port 32982/tcp
     * Modifying crontab entries for the users adm and lp
     * Scanning for other hosts running telnet (23/tcp)

   Sun has published information about the worm in the Security Sun
   Alert Feed including an inoculation script that disables the telnet
   daemon and reverses known changes made by the worm.


II. Impact

   VU#881872 allows remote attacker to log on to a vulnerable system
   via telnet and gain elevated privileges. The worm exploits this
   vulnerability to compromise systems as described above. Since the
   worm installs a backdoor shell, it is possible for an attacker with
   knowledge of the authentication tokens to access a compromised
   system and take any action with the privileges of the backdoor
   shell process, likely adm or lp.


III. Solution

Apply a patch

   To address VU#881872, apply the appropriate patches referenced in
   Sun Alert Notification 102802.

Run inoculation script

   To recover compromised systems, Sun has provided an inoculation script
   that disables the telnet daemon and reverses known changes made by the
   worm.

   Note that the inoculation script only recovers from this particular
   worm. Running the inoculation script does not guarantee system
   integrity. A vulnerable system may be compromised in different ways
   by attackers exploiting VU#881872 or using the backdoor installed
   by the worm. To fully recover, it may be necessary to rebuild a
   compromised system using trusted software sources. For more
   information, see Recovering from an Incident.


IV. Workarounds

   Until the appropriate patches can be applied, consider the
   following workarounds.

Disable telnet

   Telnet can be disabled by issuing the following command as root:

     # /usr/sbin/svcadm disable telnet

Restrict telnet access

   Restrict access to telnet (23/tcp) from untrusted networks such as
   the Internet.

Use SSH instead of telnet

   SSH provides a comparatively more secure method for remotely
   logging into a system than telnet. As general advice, we recommend
   using SSH rather than telnet.


V. References

     * US-CERT Vulnerability Note VU#881872 -
       <http://www.kb.cert.org/vuls/id/881872>

     * Recovering from an Incident -
       <http://www.cert.org/nav/recovering.html>

     * Sun Alert Notification 102802 -
       <http://sunsolve.sun.com/search/document.do?assetkey=1-26-102802-1>

     * Solaris in.telnetd worm seen in the wild + inoculation script -
       <http://blogs.sun.com/security/entry/solaris_in_telnetd_worm_seen>

     * inoculate.local -
       <http://blogs.sun.com/security/resource/inoculate.local>

     * CVE-2007-0882 -
       <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-0882>


 ____________________________________________________________________

   The most recent version of this document can be found at:

     <http://www.us-cert.gov/cas/techalerts/TA07-059A.html>
 ____________________________________________________________________

   Feedback can be directed to US-CERT Technical Staff. Please send
   email to <cert@cert.org> with "TA07-059A Feedback VU#881872" in the
   subject.
 ____________________________________________________________________

   For instructions on subscribing to or unsubscribing from this
   mailing list, visit <http://www.us-cert.gov/cas/signup.html>.
 ____________________________________________________________________

   Produced 2007 by US-CERT, a government organization.

   Terms of use:

     <http://www.us-cert.gov/legal.html>
 ____________________________________________________________________


Revision History

   February 28, 2007: Initial release


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