W32/Mytob-CK

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-CK is a mass-mailing worm and backdoor Trojan that can be controlled through the Internet Relay Chat (IRC) network.

W32/Mytob-CK may drop a file called hellmsn.exe (detected by Sophos as W32/Mytob-D) in the same location. This component attempts to spread the worm by sending the aforementioned SCR files through Windows Messenger to all online contacts.

W32/Mytob-CK is capable of spreading through email and through various operating system vulnerabilities such as LSASS (MS04-011).

The following patch for the operating system vulnerability exploited by W32/Mytob-CK can be obtained from the Microsoft website:

LSASS (MS04-011) security vulnerability

W32/Mytob-CK is capable of spreading through email and through various operating system vulnerabilities such as LSASS (MS04-011). Email sent by W32/Mytob-CK has the following properties:

Subject line:

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

Message text:

'Here are your banks documents.'
'The original message was included as an attachment.'
'The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.'
'The message contains Unicode characters and has been sent as a binary attachment.'
'Mail transaction failed. Partial message is available.'
<random characters>

The attached file consists of a base name followed by the extentions PIF, SCR, EXE or ZIP. The worm may optionally create double extensions where the first extension is DOC, TXT or HTM and the final extension is PIF, SCR, EXE or ZIP.

Sophos's anti-virus products include Genotype ™ detection technology, which can proactively protect against new threats without requiring an update. Sophos customers have been protected against W32/Mytob-CK (detected as W32/Mytob-Fam) since version 3.92. W32/Mytob-CK is a mass-mailing worm and backdoor Trojan that can be controlled through the Internet Relay Chat (IRC) network.

When first run W32/Mytob-CK copies itself to the Windows system folder as taskgmr.exe and creates the following registry entries:

HKLM\SOFTWARE\Microsoft\Ole
WINTASK
taskgmr.exe

HKCU\Software\Microsoft\Ole
WINTASK
taskgmr.exe

HKLM\SYSTEM\CurrentControlSet\Control\Lsa
WINTASK
taskgmr.exe

HKCU\SYSTEM\CurrentControlSet\Control\Lsa
WINTASK
taskgmr.exe

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
WINTASK
taskgmr.exe

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
WINTASK
taskgmr.exe

HKCU\Software\Microsoft\Windows\CurrentVersion\Run
WINTASK
taskgmr.exe

W32/Mytob-CK may drop a file called hellmsn.exe (detected by Sophos as W32/Mytob-D) in the same location. This component attempts to spread the worm by sending the aforementioned SCR files through Windows Messenger to all online contacts.

W32/Mytob-CK may also appends the following to the HOSTS file to deny access to security related websites:

127.0.0.1 www.symantec.com
127.0.0.1 securityresponse.symantec.com
127.0.0.1 symantec.com
127.0.0.1 www.sophos.com
127.0.0.1 sophos.com
127.0.0.1 www.mcafee.com
127.0.0.1 mcafee.com
127.0.0.1 liveupdate.symantecliveupdate.com
127.0.0.1 www.viruslist.com
127.0.0.1 viruslist.com
127.0.0.1 viruslist.com
127.0.0.1 f-secure.com
127.0.0.1 www.f-secure.com
127.0.0.1 kaspersky.com
127.0.0.1 www.avp.com
127.0.0.1 www.kaspersky.com
127.0.0.1 avp.com
127.0.0.1 www.networkassociates.com
127.0.0.1 networkassociates.com
127.0.0.1 www.ca.com
127.0.0.1 ca.com
127.0.0.1 mast.mcafee.com
127.0.0.1 my-etrust.com
127.0.0.1 www.my-etrust.com
127.0.0.1 download.mcafee.com
127.0.0.1 dispatch.mcafee.com
127.0.0.1 secure.nai.com
127.0.0.1 nai.com
127.0.0.1 www.nai.com
127.0.0.1 update.symantec.com
127.0.0.1 updates.symantec.com
127.0.0.1 us.mcafee.com
127.0.0.1 liveupdate.symantec.com
127.0.0.1 customer.symantec.com
127.0.0.1 rads.mcafee.com
127.0.0.1 trendmicro.com
127.0.0.1 www.microsoft.com
127.0.0.1 www.trendmicro.com

W32/Mytob-CK is capable of spreading through email and through various operating system vulnerabilities such as LSASS (MS04-011). Email sent by W32/Mytob-CK has the following properties:

Subject line:

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

Message text:

'Here are your banks documents.'
'The original message was included as an attachment.'
'The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.'
'The message contains Unicode characters and has been sent as a binary attachment.'
'Mail transaction failed. Partial message is available.'
<random characters>

The attached file consists of a base name followed by the extentions PIF, SCR, EXE or ZIP. The worm may optionally create double extensions where the first extension is DOC, TXT or HTM and the final extension is PIF, SCR, EXE or ZIP.

W32/Mytob-CK harvests email addresses from files on the infected computer and from the Windows address book as well as the Microsoft Internet Account Manager.

The following patch for the operating system vulnerability exploited by W32/Mytob-CK can be obtained from the Microsoft website:

LSASS (MS04-011) security vulnerability

Sophos's anti-virus products include Genotype ™ detection technology, which can proactively protect against new threats without requiring an update. Sophos customers have been protected against W32/Mytob-CK (detected as W32/Mytob-Fam) since version 3.92.