Backdoor.Win32.PcClient_7e321951c2

Dynamic Analysis

Payload

Behaviour	Description
WormAutorun	A worm can spread via removable drives. It writes its executable and creates "autorun.inf" scripts on all removable drives. The autorun script will execute the Backdoor's file once a user opens a drive's folder in Windows Explorer.

Process activity

The Backdoor creates the following process(es):

server.exe:488
vbc.exe:2008

The Backdoor injects its code into the following process(es):

%original file name%.exe:568
rundll32.exe:468
iexplore.exe:2040

File activity

The process iexplore.exe:2040 makes changes in the file system.

The Backdoor creates and/or writes to the following file(s):

%Documents and Settings%\%current user%\Local Settings\Temp\XxX.xXx (20496 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (48 bytes)
%Documents and Settings%\%current user%\Application Data\logs.dat (15 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\resim1078 (1614).jpg (12 bytes)

The Backdoor deletes the following file(s):

%Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (0 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\XxX.xXx (0 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (0 bytes)

The process vbc.exe:2008 makes changes in the file system.

The Backdoor creates and/or writes to the following file(s):

C:\dir\install\install\server.exe (7547 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (247 bytes)

Registry activity

The process server.exe:488 makes changes in the system registry.

The Backdoor creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "0D 6D 5C 78 08 06 C7 99 A9 E0 6C 64 49 90 FE B6"

The process %original file name%.exe:568 makes changes in the system registry.

The Backdoor creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "37 E9 A9 AA 9E 3A 0C 3A A6 9C 22 5D D1 87 72 3D"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"AppData" = "%Documents and Settings%\%current user%\Application Data"

"Cache" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files"

To automatically run itself each time Windows is booted, the Backdoor adds the following link to its file to the system registry autorun key:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"CryptedFile" = "c:\%original file name%.exe"

The process rundll32.exe:468 makes changes in the system registry.

The Backdoor creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "94 27 7E 69 B9 60 11 8A 8E F2 2C DF 81 4C FE 6F"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd73-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd72-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{b98117e8-75ca-11e2-81b2-000c293708fb}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd75-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

The process iexplore.exe:2040 makes changes in the system registry.

The Backdoor creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "94 BE 88 97 16 F1 CD C5 07 35 62 44 2F A9 E2 09"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd73-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Cookies" = "%Documents and Settings%\%current user%\Cookies"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Common Documents" = "%Documents and Settings%\All Users\Documents"

[HKCU\Software\Microsoft\Windows\ShellNoRoam\MUICache\%System%]
"shimgvw.dll" = "Windows Picture and Fax Viewer"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Desktop" = "%Documents and Settings%\%current user%\Desktop"
"Personal" = "%Documents and Settings%\%current user%\My Documents"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd72-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{b98117e8-75ca-11e2-81b2-000c293708fb}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Cache" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Common Desktop" = "%Documents and Settings%\All Users\Desktop"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd75-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\vítima]
"NewIdentification" = "vítima"
"FirstExecution" = "15/01/2014 -- 01:32"

[HKCU\Software\Microsoft\Windows\ShellNoRoam\MUICache\c:\dir\install\install]
"server.exe" = "Visual Basic Command Line Compiler"

The Backdoor modifies IE settings for security zones to map all urls to the Intranet Zone:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap]
"IntranetName" = "1"

The Backdoor modifies IE settings for security zones to map all local web-nodes with no dots which do not refer to any zone to the Intranet Zone:

"UNCAsIntranet" = "1"

The Backdoor modifies IE settings for security zones to map all web-nodes that bypassing proxy to the Intranet Zone:

"ProxyBypass" = "1"

The process vbc.exe:2008 makes changes in the system registry.

The Backdoor creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "4C ED EC 32 7F B4 25 7F 72 74 AA FB 91 27 39 24"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run]
"Policies" = "c:\dir\install\install\server.exe"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run]
"Policies" = "c:\dir\install\install\server.exe"

[HKLM\SOFTWARE\Microsoft\Active Setup\Installed Components\{680DGEC2-6TSX-1G07-CKHF-72472HP2618V}]
"StubPath" = "c:\dir\install\install\server.exe Restart"

Network activity (URLs)

No activity has been detected.

HOSTS file anomalies

No changes have been detected.

Rootkit activity

No anomalies have been detected.

Propagation

A worm can spread via removable drives. It writes its executable and creates "autorun.inf" scripts on all removable drives. The autorun script will execute the Backdoor's file once a user opens a drive's folder in Windows Explorer.

Removals

Remove it with Ad-Aware

1. Click (here) to download and install Ad-Aware Free Antivirus.
2. Update the definition files.
3. Run a full scan of your computer.

Manual removal*

1. Terminate malicious process(es) (How to End a Process With the Task Manager):

   server.exe:488
   vbc.exe:2008

2. Delete the original Backdoor file.
   
3. Delete or disinfect the following files created/modified by the Backdoor:

   %Documents and Settings%\%current user%\Local Settings\Temp\XxX.xXx (20496 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (48 bytes)
   %Documents and Settings%\%current user%\Application Data\logs.dat (15 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\resim1078 (1614).jpg (12 bytes)
   C:\dir\install\install\server.exe (7547 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (247 bytes)

4. Delete the following value(s) in the autorun key (How to Work with System Registry):

   [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   "CryptedFile" = "c:\%original file name%.exe"

5. Find and delete all copies of the worm's file together with "autorun.inf" scripts on removable drives.
   
6. Reboot the computer.
   

*Manual removal may cause unexpected system behaviour and should be performed at your own risk.

Static Analysis

Network Activity

Map

Strings from Dumps