---------- Forwarded message begins here ---------- Date: Sat, 27 Mar 1999 07:06:57 -0500 Message-Id: <199903271206.HAA17692at_private> From: CERT Advisory <cert-advisoryat_private> To: cert-advisoryat_private Subject: CERT Advisory CA-99.04 - Melissa Macro Virus Reply-To: cert-advisory-requestat_private Organization: CERT(sm) Coordination Center - +1 412-268-7090 -----BEGIN PGP SIGNED MESSAGE----- CERT Advisory CA-99-04-Melissa-Macro-Virus Original issue date: Saturday March 27 1999 Last Revised: Saturday March 27, 1999 Systems Affected * Machines with Microsoft Word 97 or Word 2000 * Any mail handling system could experience performance problems or a denial of service as a result of the propagation of this macro virus. Overview At approximately 2:00 PM GMT-5 on Friday March 26 1999 we began receiving reports of a Microsoft Word 97 and Word 2000 macro virus which is propagating via email attachments. The number and variety of reports we have received indicate that this is a widespread attack affecting a variety of sites. Our analysis of this macro virus indicates that human action (in the form of a user opening an infected Word document) is required for this virus to propagate. It is possible that under some mailer configurations, a user might automatically open an infected document received in the form of an email attachment. This macro virus is not known to exploit any new vulnerabilities. While the primary transport mechanism of this virus is via email, any way of transferring files can also propagate the virus. Anti-virus software vendors have called this macro virus the Melissa macro or W97M_Melissa virus. I. Description The Melissa macro virus propagates in the form of an email message containing an infected Word document as an attachment. The transport message has most frequently been reported to contain the following Subject header Subject: Important Message From <name> Where <name> is the full name of the user sending the message. The body of the message is a multipart MIME message containing two sections. The first section of the message (Content-Type: text/plain) contains the following text. Here is that document you asked for ... don't show anyone else ;-) The next section (Content-Type: application/msword) was initially reported to be a document called "list.doc". This document contains references to pornographic web sites. As this macro virus spreads we are likely to see documents with other names. In fact, under certain conditions the virus may generate attachments with documents created by the victim. When a user opens an infected .doc file with Microsoft Word97 or Word2000, the macro virus is immediately executed if macros are enabled. Upon execution, the virus first lowers the macro security settings to permit all macros to run when documents are opened in the future. Therefore, the user will not be notified when the virus is executed in the future. The macro then checks to see if the registry key "HKEY_Current_User\Software\Microsoft\Office\Melissa?" has a value of "... by Kwyjibo". If that registry key does not exist or does not have a value of "... by Kwyjibo", the virus proceeds to propagate itself by sending an email message in the format described above to the first 50 entries in every MAPI address book readable by the user executing the macro. Keep in mind that if any of these email addresses are mailing lists, the message will be delivered to everyone on the mailing lists. In order to successfully propagate, the affected machine must have Microsoft Outlook installed; however, Outlook does not need to be the mailer used to read the message. Next, the macro virus sets the value of the registry key to "... by Kwyjibo". Setting this registry key causes the virus to only propagate once per session. If the registry key does not persist through sessions, the virus will propagate as described above once per every session when a user opens an infected document. If the registry key persists through sessions, the virus will no longer attempt to propagate even if the affected user opens an infected document. The macro then infects the Normal.dot template file. By default, all Word documents utilize the Normal.dot template; thus, any newly created Word document will be infected. Because unpatched versions of Word97 may trust macros in templates the virus may execute without warning. For more information please see: http://www.microsoft.com/security/bulletins/ms99-002.asp Finally, if the minute of the hour matches the day of the month at this point, the macro inserts into the current document the message "Twenty-two points, plus triple-word-score, plus fifty points for using all my letters. Game's over. I'm outta here." Note that if you open an infected document with macros disabled and look at the list of macros in this document, neither Word97 nor Word2000 list the macro. The code is actually VBA (Visual Basic for Applications) code associated with the "document.open" method. You can see the code by going into the Visual Basic editor. If you receive one of these messages, keep in mind that the message came from someone who is affected by this virus and they are not necessarily targeting you. We encourage you to contact any users from which you have received such a message. Also, we are interested in understanding the scope of this activity; therefore, we would appreciate if you would report any instance of this activity to us according to our Incident Reporting Guidelines document available at: http://www.cert.org/tech_tips/incident_reporting.html II. Impact * Users who open an infected document in Word97 or Word2000 with macros enabled will infect the Normal.dot template causing any documents referencing this template to be infected with this macro virus. If the infected document is opened by another user, the document, including the macro virus, will propagate. Note that this could cause the user's document to be propagated instead of the original document, and thereby leak sensitive information. * Indirectly, this virus could cause a denial of service on mail servers. Many large sites have reported performance problems with their mail servers as a result of the propagation of this virus. III. Solutions * Block messages with the signature of this virus at your mail transfer agents. With Sendmail Nick Christenson of sendmail.com provided information about configuring sendmail to filter out messages that may contain the Melissa virus. This information is available from the follow URL: ftp://ftp.cert.org/pub/cert_advisories/Patches/CA-99-04-sendmail-m elissa-filter.txt * Utilize virus scanners Most virus scanning tools will detect and clean macro viruses. In order to detect and clean current viruses you must keep your scanning tools up to date with the latest definition files. + McAfee / Network Associates http://vil.mcafee.com/vil/vm10120.asp http://www.avertlabs.com/public/datafiles/valerts/vinfo/melissa.asp + Symantec http://www.symantec.com/avcenter/venc/data/mailissa.html + Trend Micro http://housecall.antivirus.com/smex_housecall/technotes.html * Encourage users at your site to disable macros in Microsoft Word Notify all of your users of the problem and encourage them to disable macros in Word. You may also wish to encourage users to disable macros in any product that contains a macro language as this sort of problem is not limited to Microsoft Word. In Word97 you can disable automatic macro execution (click Tools/Options/General then turn on the 'Macro virus protection' checkbox). In Word2000 macro execution is controlled by a security level variable similar to Internet Explorer (click on Tools/Macro/Security and choose High, Medium, or Low). In that case, 'High' silently ignores the VBA code, Medium prompts in the way Word97 does to let you enable or disable the VBA code, and 'Low' just runs it. Word2000 supports Authenticode on the VB code. In the 'High' setting you can specify sites that you trust and code from those sites will run. * General protection from Word Macro Viruses For information about macro viruses in general, we encourage you to review the document "Free Macro AntiVirus Techniques" by Chengi Jimmy Kuo which is available at. http://www.nai.com/services/support/vr/free.asp Acknowledgements We would like to thank Jimmy Kuo of Network Associates, Eric Allman and Nick Christenson of sendmail.com, Dan Schrader of Trend Micro, and Jason Garms and Karan Khanna of Microsoft for providing information used in this advisory. Additionally we would like to thank the many sites who reported this activity. ______________________________________________________________________ This document is available from: http://www.cert.org/advisories/CA-99-04-Melissa-Macro-Virus.html. ______________________________________________________________________ CERT/CC Contact Information Email: certat_private 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 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 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 be added to our mailing list for advisories and bulletins, send email to cert-advisory-requestat_private and include SUBSCRIBE your-email-address in the subject of your message. Copyright 1999 Carnegie Mellon University. Conditions for use, disclaimers, and sponsorship information can be found in http://www.cert.org/legal_stuff.html. * "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. ______________________________________________________________________ Revision History -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBNvy9H3VP+x0t4w7BAQG1ggP7B8ItzTRpkP2O8JK7olIOdmn072PIZZxE mJDW+A9fLDvRZQlVDSsFz/aH8ivmhor5ZbvtT14OmfIZWvxYdFnbO/s2WYL7+fV5 jL6mSb4AJ6lRXIYii+t22V0lvqJdP6VRFqy9EibpMtU2dhgFYf3TKX5e6wajOmBx bZ6Ef5jPilA= =aABH -----END PGP SIGNATURE-----
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