W32/Mytob-K

Please follow the instructions for removing worms.

Please read the instructions for removing W32/Mytob-K.

W32/Mytob-K is a mass-mailing worm and backdoor Trojan that targets users of Internet Relay Chat programs.

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

W32/Mytob-K harvests email addresses from files on the infected computer and from the Windows Address Book. W32/Mytob-K is a mass-mailing worm and backdoor Trojan that targets users of Internet Relay Chat programs.

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

When first run W32/Mytob-K copies itself to the Windows system folder as sys32.exe and creates the following registry entries:

HKCU\Software\Microsoft\OLE
WINTASK
sys32.exe

HKCU\System\CurrentControlSet\Control\Lsa
WINTASK
sys32.exe

HKCU\Software\Microsoft\Windows\CurrentVersion\Run
WINTASK
sys32.exe

HKLM\Software\Microsoft\Ole
WINTASK
sys32.exe

HKLM\System\CurrentControlSet\Control\Lsa
WINTASK
sys32.exe

HKLM\Software\Microsoft\Windows\CurrentVersion\Run
WINTASK
sys32.exe

HKLM\Software\Microsoft\Windows\CurrentVersion\RunServices
WINTASK
sys32.exe

W32/Mytob-K copies itself to the root folder as:

funny_pic.scr
my_photo2005.scr
see_this!!.scr

and creates the helper file hellmsn.exe (detected by Sophos as W32/Mytob-D) in the same location.

W32/Mytob-K 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

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

Subject line:

document
Good day
Hello
Mail Delivery System
Mail Transaction Failed
message
readme
Server Report
Status

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.

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

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-K harvests email addresses from files on the infected computer and from the Windows Address Book. The worm avoids sending email to addresses that contain the following:

.gov
.mil
accoun
acketst
admin
anyone
arin.
avp
berkeley
borlan
bsd
bsd
bugs
ca
certific
contact
example
feste
fido
foo.
fsf.
gnu
gold-certs
google
google
gov.
help
iana
ibm.com
icrosof
icrosoft
ietf
info
inpris
isc.o
isi.e
kernel
linux
linux
listserv
math
me
mit.e
mozilla
mydomai
no
nobody
nodomai
noone
not
nothing
ntivi
page
panda
pgp
postmaster
privacy
rating
rfc-ed
ripe.
root
ruslis
samples
secur
sendmail
service
site
soft
somebody
someone
sopho
submit
support
syma
tanford.e
the.bat
unix
unix
usenet
utgers.ed
webmaster
you
your