Email-Worm.Win32.Xanax

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

Any program within this subclass can have additional Trojan functions. It should also be noted that many worms use more than one method in order to spread copies via networks.

Class: Email-Worm

Email-Worms spread via email. The worm sends a copy of itself as an attachment to an email message or a link to its file on a network resource (e.g. a URL to an infected file on a compromised website or a hacker-owned website). In the first case, the worm code activates when the infected attachment is opened (launched). In the second case, the code is activated when the link to the infected file is opened. In both case, the result is the same: the worm code is activated. Email-Worms use a range of methods to send infected emails. The most common are: using a direct connection to a SMTP server using the email directory built into the worm’s code using MS Outlook services using Windows MAPI functions. Email-Worms use a number of different sources to find email addresses to which infected emails will be sent: the address book in MS Outlook a WAB address database .txt files stored on the hard drive: the worm can identify which strings in text files are email addresses emails in the inbox (some Email-Worms even “reply” to emails found in the inbox) Many Email-Worms use more than one of the sources listed above. There are also other sources of email addresses, such as address books associated with web-based email services.

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Platform: Win32

Win32 is an API on Windows NT-based operating systems (Windows XP, Windows 7, etc.) that supports execution of 32-bit applications. One of the most widespread programming platforms in the world.

Description

Technical Details

This is an Internet worm that was found in the wild in the middle of March 2001. The worm spreads via e-mail by sending infected messages from affected computers through IRC channels by sending its copy there. The worm also infects EXE files in the Windows directory.

The worm itself is a Win32 application (PE EXE file) written in Microsoft Visual C++ language. The worm size is about 60K in length, but it was found in compressed form: the worm code was compressed by ASPack utility, possessing about 34K in length.

When the worm starts, it copies itself to the Windows system directory with two names: XANAX.EXE and XANSTART.EXE. The XANSTART.EXE file is then registered in Registry auto-run key:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
Default = %winsystem%xanstart.exe

where %winsystem% is the name of the Windows system directory. As a result, the worm is run each time Windows starts up.

Infected E-mail

The worm then launches its e-mail spreading routine. To do this, the worm creates a temporary XANAX.VBS file (Visual Basic script), writes a VBS program there and starts it with the help of WSCRIPT.EXE. The VBS program gains access to the Outlook address book, and sends messages to the first 1,000 addresses from each of the address lists

Subject: Stressed? Try Xanax!
Body:

Hi there! Are you so stressed that it makes you ill? You're not alone!
Many people suffer from stress, these days. Maybe you find Prozac too
strong? Then you NEED to try Xanax, it's milder. Still not convinced?
Check out the medical details in the attached file. Xanax might change
your life!

Attachments: xanax.exe

Infecting EXE files

The worm then looks for EXE files in the Windows directory, and infects them. While infecting, the worm moves a victim file body down and writes itself to the file beginning. The worm does not infect files with names beginning with E, P, R, S, T, W.

IRC channels

Next, the worm infects the mIRC client if it is installed. The worm looks for the mIRC client in the following directories:

mirc
Program Filesmirc

on the C:, D:, E: and F: drives. If the mIRC client exists, the worm overwrites the SCRIPT.INI mIRC script file with a program that sends the worm's copy to everybody who joining the infected channel.

Other Comments

When the worm is run from a file with name with the letter 'R' as the next to last one in a file name (xxxRx.EXE), it displays the following message:

The exact name as this contains the worm's file XANSTART.EXE that is registered in the system Registry auto-run key. So, the worm displays this message upon each Windows start-up.

The worm also creates more files in the system:

Windows system directory: HOSTFILE.EXE

Windows directory: WINSTART.BAT, XANAX.SYS

The HOSTFILE.EXE remains after running an infected host file, and this file contains a pure (not infected) body of last infected file run.

The XANAX.SYS file contains the text:

Win32.HLLP.Xanax (c) 2001 Gigabyte

The WINSTART.BAT file contains commands that display the message:

Do not take this medication with ethanol, Buspar (buspirone), TCA antidepressants, narcotics, or other CNS depressants. This combination can increase CNS depression. Be sure not to take other sedative, benzodiazepines, or sleeping pills with this drug. The combinations could be fatal. Do not smoke or drink alcohol when taking Xanax. Alcohol can lower blood pressure and decrease your breathing rate to the point of unconsciousness. Tobacco and marijuana smoking can add to the sedative effects of Xanax.

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