Parent class: VirWare
Viruses and worms are malicious programs that self-replicate on computers or via computer networks without the user being aware; each subsequent copy of such malicious programs is also able to self-replicate. Malicious programs which spread via networks or infect remote machines when commanded to do so by the “owner” (e.g. Backdoors) or programs that create multiple copies that are unable to self-replicate are not part of the Viruses and Worms subclass. The main characteristic used to determine whether or not a program is classified as a separate behaviour within the Viruses and Worms subclass is how the program propagates (i.e. how the malicious program spreads copies of itself via local or network resources.) Most known worms are spread as files sent as email attachments, via a link to a web or FTP resource, via a link sent in an ICQ or IRC message, via P2P file sharing networks etc. Some worms spread as network packets; these directly penetrate the computer memory, and the worm code is then activated. Worms use the following techniques to penetrate remote computers and launch copies of themselves: social engineering (for example, an email message suggesting the user opens an attached file), exploiting network configuration errors (such as copying to a fully accessible disk), and exploiting loopholes in operating system and application security. Viruses can be divided in accordance with the method used to infect a computer:- file viruses
- boot sector viruses
- macro viruses
- script viruses
Class: Virus
Viruses replicate on the resources of the local machine. Unlike worms, viruses do not use network services to propagate or penetrate other computers. A copy of a virus will reach remote computers only if the infected object is, for some reason unrelated to the virus function, activated on another computer. For example: when infecting accessible disks, a virus penetrates a file located on a network resource a virus copies itself to a removable storage device or infects a file on a removable device a user sends an email with an infected attachment.Read more
Platform: MSWord
Microsoft Word (MS Word) is a popular word processor and part of Microsoft Office. Microsoft Word files have a .doc or .docx extension.Description
Technical Details
This macro-virus replicates under Word 8 and Word 9 (Office97 and Office2000), infects Word document and templates, and sends its copies via e-mail messages using MS Outlook. The virus is an extremely fast infector: its e-mail spreading routine may send many infected documents to different e-mail addresses when the virus installs itself into the system. The virus also has a trigger routine, changes the system registry, and disables the Word macro-virus protection.
To send its copies via e-mail messages, the virus uses VisualBasic abilities to activate other Microsoft applications and use their routines: the virus gains access to MS Outlook and summons its functions. The virus obtains the addresses from the Outlook database and sends them a new message. This massage has:
The subject: "Important Message From [UserName]" (UserName is variable)The message also has an attached document (needless to say that it is infected) - the virus attaches to the document that is being edited now (active document). As a side effect of this way of spreading, the user's documents (including confidential ones) can be sent out on the Internet.
Message body: "Here is that document you asked for ... don't show anyone else ;-)"
The virus can send very many messages: it scans Outlook AddressBook (address database), opens each list in it, and sends up to 50 messages to addresses from each one. If a list has less than 50 entries (e-mail addresses), all of them are affected. The virus sends one message per each list, the TO: field in the message contains all the addresses from this list (up to 50), and can be disregarded by anti-spam filters.
The virus sends infected e-mail only one at a time. Before sending, the virus checks system registry for its ID stamp:
HKEY_CURRENT_USERSoftwareMicrosoftOffice "Melissa?" = "... by Kwyjibo"
If this entry does not exist, the virus sends e-mail from an infected computer, and then creates this entry in the registry. Otherwise, the virus skips the e-mail routine. As a result, the virus sends infected e-mail messages only once: during subsequent attempts, it locates the "Melissa?=" entry, and skips it.
The virus is able to spread to Office2000 (Word ver.9) documents. This possibility is based on an Office "converting" feature. When new a Office version opens and loads documents and templates created by previous Word versions, it converts data in documents to new formats. The macro-program in files are also converted, including virus macros. As a result, the virus is able to replicate itself under Office2000.
In the case that the virus is run in Office2000, it performs an additional action: it disables (sets to a minimal level) Office2000 security settings (anti-virus protection).
The virus code contains one module named "Melissa" with one auto-function in it: "Document_Open" in infected documents, or "Document_Closed" in NORMAL.DOT (global macros area). The virus infects the global macros area on an infected document opening, and spreads to other documents upon their closing. To infect documents and templates, the virus copies its code line-by-line from an infected object to a "victim" one. In the case that the NORMAL.DOT is being infected, the virus names its program in the module as "Document_Close", when the virus copies its code from NORMAL.DOT to a document, the virus names it "Document_Open". As a result, the virus installs itself into the Word application at the same time the infected document is open, and infects other documents only when they are closed.
The virus also has a trigger routine that is activated if the current date is equal to the current time in minutes. Each time the virus' macros gain control, this routine inserts the text into the current document:
Twenty-two points, plus triple-word-score, plus fifty points for using
all my letters. Game's over. I'm outta here.
This text, as well as the pseudonym of the virus author, "Kwyjibo", are references to the popular "Simpsons" cartoon TV series.
The virus has the comments:
WORD/Melissa written by Kwyjibo
Works in both Word 2000 and Word 97
Worm? Macro Virus? Word 97 Virus? Word 2000 Virus? You Decide!
Word -> Email | Word 97 <--> Word 2000 ... it's a new age!
Melissa.b
This virus version transforms into a worm, not a virus: in its code, the global macros area and other documents infection routine is "commented" out (this code is present in the worm code, but all commands are disabled by "this is comment text" VisualBasic character). It is also mentioned in the author's comments in the worm's code: "We don't want to actually infect the PC, just warn them"
An infected document is attached to a message with:
Subject: "Trust No One"
Body: "Be careful what you open. It could be a virus."
When an attached document is opened, the worm-spreading routine takes control. It checks in the system registry for the "Melissa.a" mark, and if this is not present, the worm obtains one (first) address from each Outlook address list and sends new messages with itsown copy to these addresses. The worm then inserts the following text into the current document:
This could have had disasterous results. Be more careful next time you open
an e-mail. Protect yourself! Find out how at these web sites:
http://www.eos.ncsu.edu/eos/info/computer_ethics/www/abuse/wvt/worm/
http://www.nipc.gov/nipc/w97melissa.htm
http://www.cert.org/advisories/CA-99-04-Melissa-Macro-Virus.html
http://www.microsoft.com/security/bulletins/ms99-002.asp
http://www.infoworld.com/cgi-bin/displayStory.pl?990326.wcvirus.htm
Read more
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