W32/Mytob-AH

Please follow the instructions for removing worms.

Replace the Hosts file from a backup or edit it in Notepad to remove the changes that the worm has made.

You will also need to edit the following registry entries, if they are present. Please read the warning about editing the registry.

At the taskbar, click Start|Run. Type 'Regedit' and press Return. The registry editor opens.

Before you edit the registry, you should make a backup. On the 'Registry' menu, click 'Export Registry File'. In the 'Export range' panel, click 'All', then save your registry as Backup.

Locate the HKEY_LOCAL_MACHINE entries:

HKLM\Software\Microsoft\Windows\CurrentVersion\Run

HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices

and remove any reference to any file you deleted.

Each user has a registry area named HKEY_USERS\[code number indicating user]\. For each user locate the entry:

HKU\[code number]\Software\Microsoft\Windows\
CurrentVersion\Run\

and remove any reference to any file you deleted.

Close the registry editor.

W32/Mytob-AH is a mass-mailing network worm with IRC backdoor functionality.

W32/Mytob-AH will also modify the HOSTS file to prevent access to various Anti-Virus and security related websites.

W32/Mytob-AH connects to a preconfigured IRC server and joins a channel in which it can await further instructions.

W32/Mytob-AH attempts to spread to randomly-chosen IP addresses by exploiting the LSASS vulnerability (MS04-011). The patch for this vulnerability can be obtained from the Microsoft website:

MS04-011 W32/Mytob-AH is a mass-mailing network worm with IRC backdoor functionality.

W32/Mytob-AH copies itself to the file hostdrvXP.exe in the Windows system folder and creates the following registry entries in order to run at logon:

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
WINTASKMANAGER
hostdrvXP.exe

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
WINTASKMANAGER
hostdrvXP.exe

HKLM\SYSTEM\CurrentControlSet\Control\Lsa
WINTASKMANAGER
hostdrvXP.exe

HKLM\Software\Microsoft\OLE
WINTASKMANAGER
hostdrvXP.exe

HKCU\Software\Microsoft\Windows\CurrentVersion\Run
WINTASKMANAGER
hostdrvXP.exe

HKCU\SYSTEM\CurrentControlSet\Control\Lsa
WINTASKMANAGER
hostdrvXP.exe

HKCU\Software\Microsoft\OLE
WINTASKMANAGER
hostdrvXP.exe

Emails sent by W32/Mytob-AH will have the following characteristics:

Subject line: one of

Good day
hello
Mail Delivery System
Mail Transaction Failed
Server Report
Status
Error
<random text>

Message text: one of

Here are your banks documents.

The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment. The

original message was included as an attachment.

The message contains Unicode characters and has been sent as a binary attachment.

Mail transaction failed. Partial message is available.

Attached file: one of

document
readme
doc
text
file
data
test
message
body
<random text>

Attachment extension: one of

pif
scr
exe
cmd
bat

The attached file may have a double extension.

The worm will also drop hellmsn.exe into the C:\ folder and copy itself to the C:\ folder as the following files:

funny_pic.scr
my_photo2005.scr
see_this!!.scr

Sophos detects hellmsn.exe as W32/Mytob-D.

W32/Mytob-AH will also modify the HOSTS file to prevent access to various Anti-Virus and security related websites.

W32/Mytob-AH connects to a preconfigured IRC server and joins a channel in which it can await further instructions.

W32/Mytob-AH attempts to spread to randomly-chosen IP addresses by exploiting the LSASS vulnerability (MS04-011). The patch for this vulnerability can be obtained from the Microsoft website:

MS04-011