Manual Steps To Remove The Conficker.b variant

Manual steps to remove the Conficker.b variant

The following detailed steps can help you manually remove Conficker.b from a system:

1. Log on to the system by using a local account.

Important Do not log on to the system by using a Domain account, if it is possible. Especially, do not log on by using a Domain Admin account. The malware impersonates the logged on user and accesses network resources by using the logged on user credentials. This behavior allows the malware to spread.

2. Stop the Server service. This removes the Admin shares from the system so that the malware cannot spread by using this method.

Note The Server service should only be disabled temporarily while you clean up the malware in your environment. This is especially true on production servers because this step will affect network resource availability. As soon as the environment is cleaned up, the Server service can be re-enabled.

To stop the Server service, use the Services Microsoft Management Console (MMC). To do this, follow these steps:

a. Depending on your system, do the following:

§ In Windows Vista and Windows Server 2008, click Start, type services.msc in the Start Search box, and then click services.msc in the Programs list.

§ In Windows 2000, Windows XP, and Windows Server 2003, click Start, click Run, type services.msc, and then click OK.

b. Double-click Server.

c. Click Stop.

d. Select Disabled in the Startup type box.

e. Click Apply.

3. Remove all AT-created scheduled tasks. To do this, type AT /Delete /Yes at a command prompt.

4. Stop the Task Scheduler service.

o To stop the Task Scheduler service in Windows 2000, Windows XP, and Windows Server 2003, use the Services Microsoft Management Console (MMC) or the SC.exe utility.

o To stop the Task Scheduler service in Windows Vista or in Windows Server 2008, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows

a. Click Start, type regedit in the Start Search box, and then click regedit.exe in the Programs list.

b. Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule

c. In the details pane, right-click the Start DWORD entry, and then click Modify.

d. In the Value data box, type 4, and then click OK.

e. Exit Registry Editor, and then restart the computer.

5. Download and manually install security update 958644 (MS08-067). For more information, visit the following Microsoft Web site:

http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx

Note This site may be blocked because of the malware infection. In this scenario, you must download the update from an uninfected computer, and then transfer the update file to the infected system. We recommend that you burn the update to a CD because the burned CD is not writable. Therefore, it cannot be infected. If a recordable CD drive is not available, a removable USB memory drive may be the only way to copy the update to the infected system. If you use a removable drive, be aware that the malware can infect the drive with an Autorun.inf file. After you copy the update to the removable drive, make sure that you change the drive to read-only mode, if the option is available for your device. If read-only mode is available, it is typically enabled by using a physical switch on the device. Then, after you copy the update file to the infected computer, check the removable drive to see whether an Autorun.inf file was written to the drive. If it was, rename the Autorun.inf file to something like Autorun.bad so that it cannot run when the removable drive is connected to a computer.

6. Reset any Local Admin and Domain Admin passwords to use a new strong password. For more information, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/library/cc875814.aspx

7. In Registry Editor, locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost

8. In the details pane, right-click the netsvcs entry, and then click Modify.

9. Scroll down to the bottom of the list. If the computer is infected with Conficker.b, a random service name will be listed. For example, in this procedure, we will assume the name of the malware service is "gzqmiijz". Note the name of the malware service. You will need this information later in this procedure.

10. Delete the line that contains the reference to the malware service. Make sure that you leave a blank line feed under the last legitimate entry that is listed, and then click OK.

All the entries in the following list are valid. Do not delete any of these entries. The entry that must be deleted will be a randomly generated name that is the last entry in the list.

11.       AppMgmt

12.       AudioSrv

13.       Browser

14.       CryptSvc

15.       DMServer

16.       EventSystem

17.       HidServ

18.       Ias

19.       Iprip

20.       Irmon

21.       LanmanServer

22.       LanmanWorkstation

23.       Messenger

24.       Netman

25.       Nla

26.       Ntmssvc

27.       NWCWorkstation

28.       Nwsapagent

29.       Rasauto

30.       Rasman

31.       Remoteaccess

32.       Sacsvr

33.       Schedule

34.       Seclogon

35.       SENS

36.       Sharedaccess

37.       Themes

38.       TrkWks

39.       TrkSvr

40.       W32Time

41.       WZCSVC

42.       Wmi

43.       WmdmPmSp

44.       winmgmt

45.       wuauserv

46.       BITS

47.       ShellHWDetection

48.       uploadmgr

49.       WmdmPmSN

50.       xmlprov

51.       AeLookupSvc

52.       helpsvc

axyczbfsetg

53. Restrict permissions on the SVCHOST registry key so that it cannot be written to again. To do this, follow these steps.

o You must restore the default permissions after the environment has been fully cleaned.

o In Windows 2000, you must use Regedt32 to set registry permissions.

b. In Registry Editor, locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Svchost

c. Right-click the Svchost subkey, and then click Permissions.

d. In the Permissions Entry for SvcHost dialog box, click Advanced.

e. In the Advanced dialog box, click Add.

f. In the Select User, Computer or Group dialog box, type everyone, and then click Check Names.

g. Click OK.

h. In the Permissions Entry for SvcHost dialog box, select This key only in the Apply onto list, and then click to select the Deny check box for the Set Value permission entry.

i. Click OK two times.

j. Click Yes when you receive the Security warning prompt.

k. Click OK.

54. In a previous procedure, you noted the name of the malware service. In our example, the name of the malware entry was "gzqmiijz". Using this information, follow these steps:

. In Registry Editor, locate and then click the following registry subkey, where BadServiceName is the name of the malware service:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BadServiceName

For example, locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\gzqmiijz

a. Right-click the subkey in the navigation pane for the malware service name, and then click Permissions.

b. In the Permissions Entry for SvcHost dialog box, click Advanced.

c. In the Advanced Security Settings dialog box, click to select both of the following check boxes:

Inherit from parent the permission entries that apply to child objects. Include these with entries explicitly defined here.

Replace permission entries on all child objects with entries shown here that apply to child objects

55. Press F5 to update Registry Editor. In the details pane, you can now see and edit the malware DLL that loads as "ServiceDll" To do this, follow these steps:

. Double-click the ServiceDll entry.

a. Note the path of the referenced DLL. You will need this information later in this procedure. For example, the path of the referenced DLL may resemble the following:

 %SystemRoot%\System32\emzlqqd.dll

Rename the reference to resemble the following:

 %SystemRoot%\System32\emzlqqd.old

b. Click OK.

56. Remove the malware service entry from the Run subkey in the registry.

. In Registry Editor, locate and then click the following registry subkeys:

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

a. In both subkeys, locate any entry that begins with "rundll32.exe" and also references the malware DLL that loads as "ServiceDll" that you identified in step 13b. Delete the entry.

b. Exit Registry Editor, and then restart the computer.

57. Check for Autorun.inf files on any drives on the system. Use Notepad to open each file, and then verify that is a valid Autorun.inf file. The following is an example of a typical valid Autorun.inf file.

58.       [autorun]

59.       shellexecute=Servers\splash.hta *DVD*

60.       icon=Servers\autorun.ico

A valid Autorun.inf is typically 1 to 2 kilobytes (KB).

61. Delete any Autorun.inf files that do not seem to be valid.

62. Restart the computer.

63. Make hidden files visible. To do this, type the following command at a command prompt:

reg.exe add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL /v CheckedValue /t REG_DWORD /d 0x1 /f

64. Set Show hidden files and folders so you can see the file. To do this, follow these steps:

. In step 13b, you noted the path of the referenced DLL file for the malware. For example, you noted a path that resembles the following:

%systemroot%\System32\emzlqqd.dll

In Windows Explorer, open the %systemroot%\System32 directory, or the directory that contains the malware.

a. Click Tools, and then click Folder Options.

b. Click the View tab.

c. Select the Show hidden files and folders check box.

d. Click OK.

65. Select the DLL file.

66. Edit the permissions on the file to add Full Control for Everyone. To do this, follow these steps:

. Right-click the DLL file, and then click Properties.

a. Click the Security tab.

b. Click Everyone, and then click to select the Full Control check box in the Allow column.

c. Click OK.

67. Delete the referenced DLL file for the malware. For example, delete the %systemroot%\System32\emzlqqd.dll file.

68. Enable the BITS, Automatic Updates, Error Reporting, and Windows Defender services by using the Services Microsoft Management Console (MMC).

69. Turn off Autorun to help reduce the effect of any reinfection. To do this, follow these steps:

. Depending on your system, install one of the following updates:

§ If you are running Windows 2000, Windows XP, or Windows Server 2003, install update 967715. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

967715 How to correct "disable Autorun registry key" enforcement in Windows

§ If you are running Windows Vista or Windows Server 2008, install security update 950582. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

950582 MS08-038: Vulnerability in Windows Explorer could allow remote code execution

a. Note Update 953252 and security update 950582 are not related to this malware issue. These updates must be installed to enable the registry function in step 24b.

b. Type the following command at a command prompt:

reg.exe add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer /v NoDriveTypeAutoRun /t REG_DWORD /d 0xff /f

70. If the system is running Windows Defender, re-enable the Windows Defender autostart location. To do this, type the following command at the command prompt:

reg.exe add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v "Windows Defender" /t REG_EXPAND_SZ /d "%ProgramFiles%\Windows Defender\MSASCui.exe –hide" /f

71. For Windows Vista and later operating systems, the malware changes the global setting for TCP Receive Window Auto-tuning to disabled. To change this setting back, type the following command at a command prompt:

netsh interface tcp set global autotuning=normal

If, after you complete this procedure, the computer seems to be reinfected, either of the following conditions may be true:

• One of the autostart locations was not removed. For example, either the AT job was not removed, or an Autorun.inf file was not removed.
• The security update for MS08-067 was installed incorrectly

This malware may change other settings that are not addressed in this Knowledge Base article. Please visit the following Microsoft Malware Protection Center Web page for the latest details about Win32/Conficker.b:

http://www.microsoft.com/security/portal/Entry.aspx?Name=Win32/Conficker

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Verify that the system is clean

Verify that the following services are started:

• Automatic Updates (wuauserv)
• Background Intelligent Transfer Service (BITS)
• Windows Defender (windefend) (if applicable)
• Windows Error Reporting Service

To do this, type the following commands at the command prompt. Press ENTER after each command:

Sc.exe query wuauserv
Sc.exe query bits
Sc.exe query windefend
Sc.exe query ersvc

After each command runs, you will receive a message that resembles the following:

SERVICE_NAME: wuauserv
TYPE : 20 WIN32_SHARE_PROCESS
STATE : 4 RUNNING
(STOPPABLE,NOT_PAUSABLE,ACCEPTS_SHUTDOWN)
WIN32_EXIT_CODE : 0 (0x0)
SERVICE_EXIT_CODE : 0 (0x0)
CHECKPOINT : 0x0
WAIT_HINT : 0x0

In this example, "STATE : 4 RUNNING" indicates that the service is running.

To verify the status of the SvcHost registry subkey, follow these steps:

1. In Registry Editor, locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost

2. In the details pane, double-click netsvcs, and then review the service names that are listed. Scroll down to the bottom of the list. If the computer is reinfected with Conficker.b, a random service name will be listed. For example, in this procedure, the name of the malware service is "gzqmiijz".

If these steps do not resolve the issue, contact your antivirus software vendor. For more information about this issue, click the following article number to view the article in the Microsoft Knowledge Base:

49500 List of antivirus software vendors

If you do not have an antivirus software vendor, or your antivirus software vendor cannot help, contact Microsoft Consumer Support Services for more help.

After the environment is fully cleaned

After the environment is fully cleaned, do the following:

• Re-enable the Server service.
• Restore the default permissions on the SVCHOST registry key.
• Update the computer by installing any missing security updates. To do this, use Windows Update, Microsoft Windows Server Update Services (WSUS) server, Systems Management Server (SMS), System Center Configuration Manager (SCCM), or your third-party update management product. If you use SMS or SCCM, you must first re-enable the Server service. Otherwise, SMS or SCCM may be unable to update the system.