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Posted Feb 14, 2001
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CERT Advisory CA-2001-03 - The "VBS/OnTheFly" malicious code is a VBScript virus that spreads via email to users of Microsoft Outlook who have not applied previously available security updates. When the malicious code executes, it attempts to send copies of itself, using Microsoft Outlook, to all entries in each of the address books. Outlook update available here.

tags | virus
SHA-256 | 857d86f779215cacaef6a95c16b3a5b35d2bc60ec5f355777384615d79db7342


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CERT Advisory CA-2001-03 VBS/OnTheFly (Anna Kournikova) Malicious Code

Original release date: February 12, 2001
Last revised: February 12, 2001
Source: CERT/CC

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

Systems Affected

Users of Microsoft Outlook who have not applied previously available
security updates.


The "VBS/OnTheFly" malicious code is a VBScript program that spreads
via email. As of 7:00 pm EST(GMT-5) Feb 12, 2001, the CERT
Coordination Center had received reports from more than 100 individual
sites. Several of these sites have reported suffering network
degradation as a result of mail traffic generated by the
"VBS/OnTheFly" malicious code.

This malicious code can infect a system if the enclosed email
attachment is run. Once the malicious code has executed on a system,
it will take the actions described in the Impact section.

I. Description

When the malicious code executes, it attempts to send copies of
itself, using Microsoft Outlook, to all entries in each of the address
books. The sent mail has the following characteristics:

SUBJECT: "Here you have, ;o)"


Check This!

ATTACHMENT: "AnnaKournikova.jpg.vbs"

Users who receive copies of the malicious code via electronic mail
will probably recognize the sender. We encourage users to avoid
executing code, including VBScripts, received through electronic mail,
regardless of the sender's name, without prior knowledge of the origin
of the code or a valid digital signature.

It is possible for the recipients to be be tricked into opening this
malicious attachment since file will appear without the .VBS extension
if "Hide file extensions for known file types" is turned on in

II. Impact

When the attached VBS file is executed, the malicious code attempts to
modify the registry by creating the following key:

HKEY_CURRENT_USER\Software\OnTheFly="Worm made with Vbswg1.50b"

Next, the it will then place a copy of itself into the Windows


Finally, the malicious code will attempt to send separate, infected
email messages to all recipients in the Windows Address Book. Once the
mail has been sent, the malicious code creates the following registry
key to prevent future mailings of the malicious code.


The code's propagation can lead to congestion in mail servers that may
prevent them from functioning as expected.

Beyond this effect, there does not appear to be a destructive payload
associated with this malicious code. However, historical data has
shown that the intruder community can quickly modify the code for more
destructive behavior.

III. Solution

Update Your Anti-Virus Product

It is important for users to update their anti-virus software. Some
anti-virus software vendors have released updated information, tools,
or virus databases to help combat this malicious code. A list of
vendor-specific anti-virus information can be found in Appendix A.

Apply the Microsoft Outlook E-mail Security Update

To protect against this malicious code, and others like it, users of
Outlook 98 and 2000 may want to install the Outlook E-mail Security
update included in an Outlook SR-1. More information about this update
is available at


You may also find the following document on Outlook security useful


The Outlook E-mail security update provides features that can prevent
attachments containing executable content from being displayed to
users. Other types of attachments can be configured so that they must
be saved to disk before they can be opened (or executed). These
features may greatly reduce the chances that a user will incorrectly
execute a malicious attachment.

Filter the Virus in Email

Sites can use email filtering techniques to delete messages containing
subject lines known to contain the malicious code, or can filter
attachments outright.

Exercise Caution When Opening Attachments

Exercise caution when receiving email with attachments. Users should
disable auto-opening or previewing of email attachments in their mail
programs. Users should never open attachments from an untrusted
origin, or that appear suspicious in any way. Finally, cryptographic
checksums should also be used to validate the integrity of the file.

IV. General protection from email Trojan horses and viruses

Some previous examples of malicious files known to have propagated
through electronic mail include:

Melissa macro virus - discussed in CA-99-04

False upgrade to Internet Explorer - discussed in CA-99-02

Happy99.exe Trojan Horse - discussed in IN-99-02

CIH/Chernobyl virus - discussed in IN-99-03

In each of the above cases, the effects of the malicious file are
activated only when the file in question is executed. Social
engineering is typically employed to trick a recipient into executing
the malicious file. Some of the social engineering techniques we have
seen used include

* Making false claims that a file attachment contains a software
patch or update
* Implying or using entertaining content to entice a user into
executing a malicious file
* Using email delivery techniques that cause the message to appear
to have come from a familiar or trusted source
* Packaging malicious files in deceptively familiar ways (e.g., use
of familiar but deceptive program icons or file names)

The best advice with regard to malicious files is to avoid executing
them in the first place. CERT advisory CA-1999-02.html and the
following CERT tech tip discuss malicious code and offers suggestions
to avoid them.



Appendix A. - Vendor Information

Appendix A. Anti-Virus Vendor Information

Aladdin Knowledge Systems


Command Software Systems, Inc.


Computer Associates




Finjan Software, Ltd.




Dr. Solomon, NAI






Trend Micro


You may wish to visit the CERT/CC's Computer Virus Resources Page
located at:


This document was written by Cory Cohen, Roman Danyliw, Ian Finlay,
John Shaffer, Shawn Hernan, Kevin Houle, Brian B. King, and Shawn Van

This document is available from:

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

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


If you prefer to use DES, please call the CERT hotline for more

Getting security information

CERT publications and other security information are available from
our web site


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

subscribe cert-advisory

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

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 2001 Carnegie Mellon University.

Revision History
February 12, 2001: Initial release

Version: PGP for Personal Privacy 5.0
Charset: noconv

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