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Glossary

Win32/Conficker.AX

Aliases:	Trojan-Ransom.Win32.XBlocker.zu (Kaspersky), W32.Downadup (Symantec), Ransom!cn trojan (McAfee)
Type of infiltration:	Worm
Size:	212438 B
Affected platforms:	Microsoft Windows
Signature database version:	5109 (20100512)

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Short description

Win32/Conficker.AX is a worm that spreads via shared folders and removable media. It connects to remote machines in attempt to exploit the Server Service vulnerability.

Installation

When executed, the worm copies itself in some of the the following locations:

%system%%variable%.dll
%programfiles%Internet Explorer%variable%.dll
%programfiles%Movie Maker%variable%.dll
%appdata%%variable%.dll
%temp%%variable%.dll

A string with variable content is used instead of %variable%.

The worm loads and injects the %variable%.dll library into the following processes:

explorer.exe
services.exe
svchost.exe

The worm registers itself as a system service with the name combined from the following strings:

Boot
Center
Config
Driver
Helper
Image

In order to be executed on every system start, the worm sets the following Registry entry:

[HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
Run]
"%variable_name%" = "rundll32.exe
"%system%%variable%.dll",%random_string%"

The following Registry entries are set:

[HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServices
%random service name%Parameters]
"ServiceDll" = "%system%%variable%.dll"
[HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServices
%random service name%]
"Image Path" = "%System Root%system32svchost.exe -k
netsvcs"
"DisplayName" = "%variable service name%"
"Type" = 32
"Start" = 2
"ErrorControl" = 0
"ObjectName" = "LocalSystem"
"Description" = "%variable_name%"

A string with variable content is used instead of %random service name%.

Spreading

The worm starts a HTTP server on a random port.

By connecting to remote machines to port TCP 139, 445 it tries to exploit the Server Service.

If successful, the remote computer attempts to connect to the infected computer and download a copy of the worm .

It is a DLL library with the following extension:

.bmp
.gif
.jpeg
.png

This vulnerability is described in Microsoft Security Bulletin MS08-067 .

Spreading via shared folders

The worm tries to copy itself into shared folders of machines on a local network.

The following usernames are used:

%username%

The following passwords are used:

123
1234
12345
123456
1234567
12345678

The following filename is used:

\%hostname%ADMIN$System32%variable%.dll

The worm schedules a task that causes the following file to be executed daily:

rundll32.exe %variable%.dll, %random_string%

Spreading on removable media

The worm copies itself into existing folders of removable drives.

The following filename is used:

%drive%RECYCLERS-%variable1%%variable2%.%variable3%

A string with variable content is used instead of %variable1-3%.

The worm creates the following file:

%drive%autorun.inf

Thus, the worm ensures it is started each time infected media is inserted into the computer.

Other information

The following services are disabled:

Windows Security Center Service (wscsvc)
Windows Automatic Update Service (wuauserv)
Background Intelligent Transfer Service (BITS)
Windows Defender Service (WinDefend)
Windows Error Reporting Service (ERSvc)
Windows Error Reporting Service (WerSvc)

The worm launches the following processes:

netsh interface tcp set global autotuning=disabled

The worm blocks access to any domains that contain any of the following strings in their name:

ahnlab
arcabit
avast
avira
castlecops
centralcommand

The worm will attempt to download several files from the Internet. The files are then executed.

The worm runs only encrypted and properly signed files.

These are stored in the following locations:

%temp%%variable%.tmp

A string with variable content is used instead of %variable%.

The worm may set the following Registry entries:

[HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServices
SharedAccessParametersFirewallPolicyStandardProfile
GloballyOpenPortsList]
"%port number%:TCP" = "%port
number%:TCP:*:Enabled:%variable%"

The performed command creates an exception in the Windows Firewall.

The worm connects to the following addresses:

http://checkip.dyndns.org
http://www.whatismyip.org
http://www.whatsmyipaddress.com
http://www.getmyip.org
http://baidu.com
http://google.com

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