CERT Advisory CA-2004-02 Email-borne Viruses

28/01/04, CERT Advisory CA-2004-02 Email-borne Viruses
From: CERT Advisory <cert-advisory@cert.org>

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To: cert-advisory@cert.org
Subject: CERT Advisory CA-2004-02 Email-borne Viruses
From: CERT Advisory <cert-advisory@cert.org>
Date: Tue, 27 Jan 2004 12:27:28 -0500
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Mail-from: From cert-advisory-owner@cert.org Wed Jan 28 01:10:29 2004
Organization: CERT(R) Coordination Center - +1 412-268-7090

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CERT Advisory CA-2004-02 Email-borne Viruses

   Original release date: January 27, 2004
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

     * Any system running Microsoft Windows (all versions from Windows 95
       and  up) and used for reading email or accessing peer-to-peer file
       sharing services.

Overview

   In  recent weeks there have been several mass-mailing viruses released
   on  the  Internet.  It  is important for users to understand the risks
   posed  by  these  pieces  of malicious code and the steps necessary to
   protect their systems from virus infection.

I. Description

   Over  the  past  week,  we  have  seen  two more mass-mailing viruses,
   W32/Bagle  and  W32/Novarg,  impact a significant number of home users
   and  sites.  The technology used in these viruses is not significantly
   different  from  prior  mass-mailing  viruses  such  as  W32/Sobig and
   W32/Mimail. Unsolicited email messages containing attachments are sent
   to  unsuspecting  recipients.  They  may  contain  a return address, a
   provocative  envelope,  or something else that encourages its receiver
   to  open  it.  This technique is called social engineering. Because we
   are  trusting  and curious, social engineering is often effective. The
   widespread  impact  of  these  latest  viruses,  which  rely  on human
   intervention  to  spread,  demonstrates  the  effectiveness  of social
   engineering.
       
   It  continues  to  be  important to ensure that anti-virus software is
   used  and  updated  regularly,  that  attachments are examined on mail
   servers,  and  that  firewalls filter unneeded ports and protocols. It
   also  remains  necessary  that  users be educated about the dangers of
   opening attachments, especially executable attachments.

       CERT Incident Note IN-2004-01 - W32/Novarg
       http://www.cert.org/incident_notes/IN-2004-01.html

       CERT Incident Note IN-2003-03 - W32/Sobig.F
       http://www.cert.org/incident_notes/IN-2003-03.html

       CERT Incident Note IN-2003-02 - W32/Mimail
       http://www.cert.org/incident_notes/IN-2003-02.html

II. Impact

   A  virus  infection  can have significant consquences on your computer
   system. These consequences include, but are not limited to:

     * Information  disclosure  -  Mass-mailing viruses typically harvest
       email  addresses  from  the  addressbooks  or  files  found  on an
       infected system. Some viruses will also attempt to send files from
       an  infected  host  to other potential victims or even back to the
       virus author. These files may contain sensitive information.

     * Add/Modify/Delete  files  -  Once a system is compromised, a virus
       could  potentially  add,  modify  or delete arbitrary files on the
       system.  These  files  may  contain  personal  information  or  be
       required for the proper operation of the computer system.

     * Affect  system stability - Viruses can consume significant amounts
       of  computer  resources  causing  a  system  to  run  slowly or be
       rendered unusable.

     * Install  a  backdoor  - Many viruses will install a backdoor on an
       infected system. This backdoor may be used by a remote attacker to
       gain  access to the system, or view/add/modify/delete files on the
       system.  These  backdoors  may  also  be leveraged to download and
       control  additional tools for use in distributed denial-of-service
       (DDoS) attacks against other sites.

     * Attack  other systems - Systems infected by viruses are frequently
       used  to  attack  other  systems. These attacks frequently involve
       attempts  to  exploit  vulnerabilities  on  the  remote systems or
       denial-of-service  attacks  that  utilize a high volume of network
       traffic.

     * Send  unsolicited  bulk  email  (spam) to other users - There have
       been  numerous  reports of spammers leveraging compromised systems
       to  send  unsolicited  bulk  email.  Frequently  these compromised
       systems  are  poorly  protected end user computers (e.g., home and
       small business systems).

III. Solution

   In  addition  to  following  the  steps  outlined in this section, the
   CERT/CC  encourages  home  users to review the "Home Network Security"
   and "Home Computer Security" documents.

       Home Network Security
       http://www.cert.org/tech_tips/home_networks.html

       Home Computer Security
       http://www.cert.org/homeusers/HomeComputerSecurity/

Run and maintain an anti-virus product

   While  an up-to-date antivirus software package cannot protect against
   all  malicious  code, for most users it remains the best first line of
   defense  against  malicious  code  attacks.  Users  may  wish  to read
   IN-2003-01  for  more  information on anti-virus software and security
   issues.

       CERT Incident Note IN-2003-01
       http://www.cert.org/incident_notes/IN-2003-01.html

   Most   antivirus   software   vendors   release   frequently   updated
   information, tools, or virus databases to help detect and recover from
   malicious  code.  Therefore,  it  is  important  that users keep their
   antivirus software up to date. The CERT/CC maintains a partial list of
   antivirus vendors.
   
       Computer Virus Resources
       http://www.cert.org/other_sources/viruses.html

   Many   antivirus   packages   support   automatic   updates  of  virus
   definitions. The CERT/CC recommends using these automatic updates when
   available.

Do not run programs of unknown origin

   Do  not  download,  install, or run a program unless you know it to be
   authored by a person or company that you trust.

   Email users should be wary of unexpected attachments. Be sure you know
   the  source  of an attachment before opening it. Also remember that it
   is  not  enough  that  the  mail  originated from an email address you
   recognize.  The  Melissa  virus spread precisely because it originated
   from a familiar email address.

   Users  should also be wary of URLs in email messages. URLs can link to
   malicious  content  that  in  some  cases may be executed without user
   intervention.   A   common   social  engineering  technique  known  as
   "phishing" uses misleading URLs to entice users to visit malicious web
   sites.  These  sites  spoof  legitimate web sites to solicit sensitive
   information such as passwords or account numbers.

   In  addition,  users  of  Internet Relay Chat (IRC), Instant Messaging
   (IM),  and  file-sharing  services  should  be particularly careful of
   following links or running software sent to them by other users. These
   are commonly used methods among intruders attempting to build networks
   of distributed denial-of-service (DDoS) agents.

Use a personal firewall

   A  personal  firewall will not necessarily protect your system from an
   email-borne  virus,  but  a  properly configured personal firewall may
   prevent  the virus from downloading additional components or launching
   attacks  against  other  systems.  Unfortunately,  once on a system, a
   virus may be able to disable a software firewall, thus eliminating its
   protection.

Email gateway filtering

   Depending  on your business requirements, it is advisable to configure
   filtering  of  specific  file  extensions  of email attachments at the
   email  gateway. This filtering should be configured carefully, as this
   may  affect  legitimate  attachments  as  well. It is recommended that
   attachments  are  quarantined  for  later  examination and/or possible
   retrieval.

Recovering from a system compromise

   If  you  believe  a  system under your administrative control has been
   compromised, please follow the steps outlined in

       Steps for Recovering from a UNIX or NT System Compromise
       http://www.cert.org/tech_tips/win-UNIX-system_compromise.html
     _________________________________________________________________

   Authors: Jeff Carpenter, Chad Dougherty, Jeff Havrilla, Allen
   Householder, Brian King, Marty Lindner, Art Manion, Damon Morda, Rob
   Murawski
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2004-02.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: cert@cert.org
          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
          U.S.A.

   CERT/CC   personnel   answer  the  hotline  08:00-17:00  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
   http://www.cert.org/CERT_PGP.key

   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
   http://www.cert.org/

   To  subscribe  to  the CERT mailing list for advisories and bulletins,
   send  email  to majordomo@cert.org. Please include in the body of your
   message

   subscribe cert-advisory

   *  "CERT"  and  "CERT  Coordination Center" are registered in the U.S.
   Patent and Trademark Office.
   ______________________________________________________________________

   NO WARRANTY
   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.
   ______________________________________________________________________

   Conditions for use, disclaimers, and sponsorship information

   Copyright 2004 Carnegie Mellon University.

   Revision History
   January 27, 2004:  Initial release

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