W32/Mytob.B is a mass mailing worm. This worm is a variant of W32/Mytob.A. The worm will infect Windows systems and spreads through email.

The infected email carries a spoofed 'From' address picked up randomly from the infected system.

The subject of the infected mail will be any one of the following;

Good day
hello
status
test
Mail Transaction Failed
error
Server Repoer
Mail Delivery System
(Blank Subject)
(Variable String)

The infected attachment will be any one of the following;

message
document
doc
body
data
file
test
text
readme
(Variable String)

The extension of the infected attachment will be single or double, The first extension can be any one of these;

doc, htm, txt.

The second extension can be any one of these;

bat, pif, exe, scr, zip.

The body of the infected mail will be any one of the following;

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

Mail transaction failed. Partial message is available.

test

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

(Blank Body)

(Variable String)

Upon execution of the infected attachment, the worm copies itself as wfdmgr.exe in the Windows System folder.

The worm modifies registry at the following location to load itself during each startup.

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

To propagate itself, the worm scans the files having the following extensions and collects all the domain names from the infected system.

adb, asp, dbx, htm, php, pl, sht, tbb, wab.

The worm generates email addresses using one of the following names as the prefix before '@' and the suffix as one of the domain names collected.

adam, alex, alice, andrew, anna, bill, bob, brenda, brent, brian, claudia, dan, dave, david, debby, fred, george, helen, jack, james, jane, jerry, jim, jimmy, joe, john, jose, julie, kevin, leo, linda, maria, mary, matt, michael, mike, peter, ray, robert, sam, sandra, serg, smith, stan, steve, ted, tom

The worm attempts to locate SMTP server by appending the following prefixes to the domain names collected from the infected system. On successful SMTP server access it mails itself to the produced email addresses.

mx.
ns.
relay.
mail1.
mxs.
mx1.
smtp.
mail.
gate.

This worm first appeared on 28th February, 2005.

 Other names of W32/Mytob.B Worm:

This Worm is also known as W32/Mytob.B.worm, W32.Mytob.C@mm, Net-Worm.Win32.Mytob.b.