Mailissa virus info
Gary Williams
(Norton Antivirus) Virus Encyclopedia. It took more than 10 minutes
to get the page downloaded, since so many people are looking at it!
So I'm copying it to you. I suspect that if you don't have MS Word 97
you're imune...
-- Gary
W97M.Melissa.A (W97M.Mailissa)
VirusName: W97M.Melissa.A
Aliases: W97M.Mailissa
Infection Length: one VBA5 module named Melissa
Area of Infection: Microsoft Word 97 documents
Likelihood: Common
Region Reported: Worldwide
Characteristics: Macro, Wild
Description:
W97M.Melissa.A (also known as W97M.Mailissa) is a typical macro
virus which has an unusual payload. When a user opens an infected
document, the virus will attempt to e-mail a copy of this document to up
to
50 other people, using Microsoft Outlook.
Similar to W97M.Pri, the virus turns off the security protection upon
opening an infected document in MS Word 2000. This disables MS Word
2000 macro prompt the next time the document is opened.
It infects a MS Word 97 and MS Word 2000 document by adding a new
VBA5 (macro) module named Melissa. Although there is nothing unique in
the infection routine of this macro virus, it has a payload that
utilizes MS
Outlook to send an attachment of the infected document being opened.
Payload
s its primary payload, the virus will attempt to use Microsoft Outlook
to
e-mail a copy of the infected document to up to 50 other people. When a
user opens or closes an infected document, the virus first checks to see
if it
has done this mass e-mailing once before, by checking the following
registry key:
"HKEY_CURRENT_USER\Software\Microsoft\Office\" as "Melissa?"
value.
If this key has a value "Melissa?" set to the value "...by Kwyjibo",
then the
mass e-mailing has been done previously from the current machine. The
virus will not attempt to do the mass mailing a second time, if it has
already
been done from this machine.
If it does not find the registry entry, the virus does the following:
1.Open MS Outlook.
2.Using MAPI calls, it gets the user profile to use MS Outlook.
3.It creates a new e-mail message to be sent to up to 50
addresses
listed in the user's MS Outlook address book.
4.It gives the email message a subject line:
"Important Message From USERNAME",
where USERNAME is taken from MS Word setting.
5.The body of the email message is:
"Here is that document you asked for ... don't show anyone
else ;-)"
6.It attaches the active document (the infected document being
opened or closed) to the email message.
7.It sends the e-mails.
Please note that "HKEY_CURRENT_USER\Software\Microsoft\Office"
is a registry entry created by MS Office. The virus simply adds the new
value "Melissa?" into this registry entry. This value is set to "…by
Kwyjibo"
if the virus has previously e-mailed an infected document from the
system.
Once the value is set, the virus will not attempt another mass mailing
from
the same machine.
There is a second payload which triggers once an hour, at the number of
minutes past the hour corresponding to the date (i.e., on the 16th of
the
month, the payload triggers at 16 minutes after every hour). If an
infected
document is opened or closed at the appropriate minute, this payload
will
insert the following sentence into the document:
" Twenty-two points, plus triple-word-score, plus fifty points
for using all my letters. Game's over. I'm outta here."
Note that the virus will also infect other documents on the user's
machine,
using the normal infection mechanisms of macro viruses, even if the user
does not have MS Outlook. So, it is potentially possible for a new
document from any user's machine to be e-mailed to other people through
the following steps:
1.User opens Document 1 containing W97M.Melissa.A infection.
2.W97M.Melissa.A also infects a new Document 2 on the user's
machine (even if the user does not have MS Outlook).
3.User e-mails Document 2 to another person who has not previously
been infected by W97M.Melissa.A and who does have MS
Outlook.
4.When that second person opens the infected Document 2 on their
machine, the document will be e-mailed to 50 people via MS
Outlook.
Hiding its activity:
Similar to most macro viruses, this macro virus tries to hide its
activity by
disabling the following menu items:
Tools-Macro in MS Word 97
By disabling this menu command, the virus prevents any user from
listing the macro / VBA module in MS Word 97 to manually check
for infection.
Macro-Security in MS Word 2000
By disabling this menu command, it prevents the user from changing
the security level in MS Word 2000.
To hide its infection activity, it also disables the following options
in MS
Word 97:
Prompt to save Normal template
Confirm conversion at Open
Macro virus protection
With these options disabled, MS Word 97 does not warn or prompt while
saving the NORMAL.DOT or while opening a document with macros in it.
Repair Notes:
Norton AntiVirus users can protect themselves from this virus by
downloading the current virus definitions either through LiveUpdate or
from
the following webpage:
http://www.symantec.com/avcenter/download.html
Write-up by: Raul K. Elnitiarta
March 29, 1999
Here's the link where I got this:
href:http://www.symantec.com/avcenter/venc/data/mailissa.html
-- Gary
----
Even if (like me) you don't have Norton Anti-cirus, the site
accessible via this page is a good one for virus info.