Email-Worm.Win32.Puron

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 a virus-worm that spreads via infected e-mails, and infects Windows EXE files on computers. The worm's routines have bugs, and in some cases, halt the computer and/or corrupt files while infecting them.

The worm code has the "copyright" text strings:

(c)Vecna
Vecna is a punk rocker now...

Infected File Run

The worm can enter a computer via infected e-mails from the local network or from any other infected file that is executed.

When the worm starts, it extracts from an infected file its "main" code (that is "pure" virus code - Win32 PE EXE file 9.5 Kb of size), saves it to the Windows TEMP directory with a randomly selected name (for example, LNBAMKON.EXE, MMCAAHAN.EXE) and executes that file.

When the virus' "main" code gains control, it moves its file to the Windows directory that is referenced in the Registry key:

HKLMSOFTWAREMicrosoftWindowsCurrentVersionExplorerShell Folders
Common Startup = %startup%

The %startup% directory name depends in Windows version, for example:

Documents and SettingsAll UsersStart MenuProgramsStartup
%WindowsDir%All UsersStart MenuProgramsStartup

The worm moves itself to that %startup% directory with a random name that has eight randomly selected digits and an .EXE extension, for example:

00544102.EXE
17060133.EXE
37154273.EXE

The worm then executes that copy in the "Startup" directory, and deletes the first copy in the Windows TEMP directory, for example:

C:VIRUS.EXE - infected file is run
C:WINDOWSTEMPMMCAAHAN.EXE - 1st copy is created and run
C:WINDOWSAll UsersStart MenuProgramsStartup0544102.EXE - this is 2nd copy, it is created here and executed. The 1st copy is deleted then.

Because of a bug, in some cases, the worm crashes in the middle of this process, and the 1st copy is left in the TEMP directory.

When this "file moving" process is complete, the worm installs a "stealth" hook, and runs the infection and e-mail spreading routines.

Infection

The infection routine when gains control, searches for a .EXE and .SCR Windows executable file on all local and network drives, and infects them. While infecting, it obtains a block from the file middle, compresses it, and stores the compressed data and worm code in the file so that the file length does not increase.

The worm also uses a polymorphic mutation engine to make the detection and disinfection process more complex.

E-mail spreading

To spread itself, the worm connects to a SMTP mail server, and sends infected messages to e-mail addresses. Both the SMTP server name and e-mail addresses, the worm obtains from WAB data files (Windows Address Book).

The infected messages are of HTML format and have fields:

From: "Mondo bizarro" [mourning@obituary.org]
Subject: Joey is dead, man... :-(
Text: A tribute to Joey Ramone (1951-2001)
Attach: ramones.mp3.exe

The worm uses one of the security vulnerabilities (Vulnerability identifier: CAN-2001-0154) that were found in MS Windows in 2001. The result of this breach is the possibility of spawning an attached EXE file without a user's action. When an infected e-mail is opened for reading or preview, the worm's EXE file is automatically run.

Microsoft already has released a patch that eliminates this vulnerability. Additional information may be found here: http://www.microsoft.com/technet/security/bulletin/MS01-020.asp

Stealth

The worm hooks FindFile and FindProcess Windows system calls (FindFirstFileA, FindNextFileA, Process32First, Process32Next). The worm processes these calls so that its copy in the "startup" directory (see above) is not reported. As a result, the worm file is not visible in files and processes lists.

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