Email-Worm.Win32.Sysid

Class Email-Worm
Platform Win32
Description

Technical Details

This is an Internet worm that spreads in infected e-mails by using MS Outlook. The worm itself is a Windows executable written in Delphi and compressed by Aspack PE EXE compression utility. The worm’s file size (compressed) is about 200K, the original (uncompressed) size is about 400K.

The worm installs itself into the system, and then periodically accesses MS Outlook and sends infected messages. There are no payload routines found in the worm code.

The worm hides its activity pretending to be a “Personal ID Generator” utility. This utility uses strings in Chinese coding, so it cannot be truly visible under non-Chinese Windows.

At the same time as the worm displays the “Personal ID Generator” window, it installs itself into Windows. To do this, it gets the names of the Windows and Windows system directories and copies itself to there with the “SYSID.EXE”
name. In case the worm cannot detect the Windows directory, it uses hard-coded names:

C:WINNTSYSTEM32SYSID.EXE
C:WINNTSYSID.EXE
C:WINDOWSSYSTEMSYSID.EXE
C:WINDOWSSYSID.EXE

To run each time Windows starts, the worm registers its copy in the system registry in the auto-run section:

HKLMSoftwareMicrosoftWindowsCurrentVersionRun
WindowsVersion = “sysid”

The worm uses a trick to hide this record. Upon being activated, the worm deletes that record from the registry, and upon exiting, restores it. To stay active as long as possible, the worm leaves its copy in the Windows memory as
a hidden application (service). So the worm is active up to the moment Windows is shut down, and worm’s record in the system registry is not visible. At the moment Windows is shut down, the worm restores the registry record.

As a result, the worm record cannot be read by standard RegEdit – it simply does not exist when Windows has completed its start-up procedure, and up to the moment Windows is rebooted:

  • Upon each restart, Windows gets a worm file name from the system registry and runs it; the worm then deletes that record and stays in the system memory awaiting Windows restart. At that moment, the worm’s registry record does not exist.
  • Upon Windows shut down, the worm restores its registry record, and it is ready to run the worm again upon the next Windows restart. At that moment, the registry record exists, but it cannot be read by standard utilities.

To spread via e-mail messages, the worm runs a file helper. This file is a VisualBasicScript application, and is created by the worm in the Windows system directory with the WINVER.VBS name. The VBS program in this file gains access to MS Outlook, obtains randomly selected names from the AddressBook, and creates and sends messages to these addresses. The number of addresses infected depends on the total number of addresses in the AddressLists. In case there is less than 200
addresses, the worm sends messages to 10% of them; otherwise, (more than 200 messages) the worm sends infected e-mails to 2% of them.

The infected message body is empty. The message Subject is randomly selected from all subject variants found in the “Sent items” Outlook list.

The message has four attached files. First is the worm EXE copy with a name randomly selected from 100 variants (see below); second, the attached file is randomly selected from .JPEG, .JPG, .DOC and .XLS files found in “C:My
Documents” folder. Two other attached files are e-mail messages randomly selected from the “Sent items” list.

The list of possible worm EXE names appears as follows:

pdd2000.exe
Tools.exe
Pcc99.exe
98fix.exe
Book.exe
Phone.exe
Car.exe
Game.exe
Office98fix.exe
Graphics.exe
ScreenSaver.exe
Joke.exe
Window.exe
Mp3Player.exe
WinAmp.exe
Mouse.exe
FTP_Pro.exe
WWW.exe
Ghost7.exe
MazeGame.exe
3DS.exe
Source.exe
Action.exe
Color.exe
Color_Joke.exe
GameStyle.exe
HAHA.exe
MyResume.exe
EasyGame.exe
Jonny.exe
BallGame.exe
MazeGame.exe
MAC9.exe
Desk_Demo.exe
Girl.exe
GirlGame.exe
GoodGame.exe
FreedMan.exe
Hurry Up.exe
Take a Rest.exe
Take Easy.exe
Do not over time.exe
Meeting.exe
Milk.exe
PlayBoy.exe
BadGirl.exe
BadBoy.exe
PenHouse.exe
Tape.exe
Display.exe
Click Me.exe
Apple.exe
New Product Show.exe
My Resume.exe
Boss Game.exe
Boy and Girl.exe
WinZip9.exe
Good Job.exe
New Language.exe
Key User.exe
My Letter.exe
My Sister.exe
My Mother.exe
My Father.exe
My Picture.exe
Merry.exe
Happy.exe
Happy New Year.exe
How Are You.exe
586 Tech.exe
Cell Phone.exe
Sex Picture.exe
The Young King.exe
Oscar.exe
The Happy Prince.exe
The Star Child.exe
Question.exe
Issues For Today.exe
Acknowledgments.exe
Game99.exe
True or False.exe
Good Art.exe
News.exe
Stock News.exe
Music.exe
MP3.exe
Choose Games.exe
Life-Styles.exe
Life-Cycles.exe
Sometimes.exe
Summary.exe
Market.exe
MP3 Tools.exe
Cheat.exe
New Joke.exe
New System.exe
New Job.exe
New Chance.exe
Make More Money.exe
Help Yourself.exe