Name :	Yanz.A
Category:	Virus
Type:	Virus
Platform:	Win32

Yanz is an mass-mailing worm. It sends email messages that
contain texts and attachment names related to the Asian singer
Stefanie Sun (Yanzi). The worm can also spread to shared folders
of local network and peer-to-peer clients.

The worm's file is a PE executable file about 102 kilobytes long. The file is not packed.


Installation to system


When the worm's file is run for the first time, it shows a fake messagebox:

HATA

KERNEL HATASI



Then the worm copies itself to Windows System directory as LSASSS.EXE and as YANZI.EXE and creates a startup key for the first file in System Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
"Microsoft Kernel" = "%WinSysDir%\lsasss.exe"

where %WinSysDir% represents Windows System folder, for example 'c:\windows\system32' for default Windows XP installation.

Also the worm creates a ZIP archive named YanZi.zip with the worm's file named 'Sun YanZi.pif' in Windows folder. The worm uses 'store' method to create a ZIP archive meaning that the worm's file inside the archive is not compressed.

The worm creates a short HTML file named 'sun_yanzi.htm' in the current directory and writes 'Sun-Yanzi' text string there.

Additionally the worm creates 2 base64-encoded files in Windows System folder:


The first file is a base64-encoded copy of the worm, the second one is a base64-encoded copy of the worm in a ZIP archive. These files are used during spreading of the worm in e-mails.

The worm creates a mutex with the name 'Sun YanZi - forever'.


Spreading in e-mails

Before spreading the worm reads user's Address Book and scans a hard drive to harvert victims' e-mail addresses. The worm scans files with the following extensions:


The worm ignores e-mail addresses if they contain any of the following substrings:


The worm sends e-mails with different subjects, body texts and attachment names. The subject of an infected e-mail is selected from the following variants:


The body text of an infected e-mail is selected from the following variants:


The attachment is either a ZIP archive with the worm's executable file or the worm's executable file itself. The name of an infected attachment is selected from the following variants:


The extension of an infected attachment can be:


Spreading to shared folders


The worm scans all available hard drives and ram disks. If it finds a folder with the name that contains 'shar' substring, it copies itself there with the following names:


This way the worm can spread to shared folders of P2P (peer-to-peer) clients and to local network.

Backdoor


The worm has a simple backdoor that listens on TCP port 67. It allows to download and run executable files from Internet.

Payload

During its installation cycle the worm kills the following processes: