Backdoor.Win32.PcClient_12db8bd48e

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:1620
vbc.exe:1064

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

%original file name%.exe:2016
rundll32.exe:1488
iexplore.exe:1248

File activity

The process iexplore.exe:1248 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 (16360 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (32 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\1535376_10151795168026610_658562497_n.jpg (32 bytes)
%Documents and Settings%\%current user%\Application Data\logs.dat (15 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:1064 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 (268 bytes)

Registry activity

The process %original file name%.exe:2016 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "AD 17 82 FE F6 54 7D 65 F1 B0 62 EF 97 63 2C 4D"

[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 server.exe:1620 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "78 0C 10 0C EB 2E 2D 61 1A F3 10 20 AB 19 24 16"

The process rundll32.exe:1488 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "71 98 7F DE 32 07 7E 14 71 C5 EB 48 DC 8A 6F 59"

[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:1248 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "EA D0 14 BA AF A8 6E FF 00 15 ED 26 23 8D E1 6D"

[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" = "16/01/2014 -- 07:41"

[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:1064 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "13 D6 37 24 DA D3 4B C6 66 4A 97 47 64 C7 EF 96"

[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\{SX78G460-285D-P227-J720-B08L6SK5431W}]
"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:1620
   vbc.exe:1064

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 (16360 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (32 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\1535376_10151795168026610_658562497_n.jpg (32 bytes)
   %Documents and Settings%\%current user%\Application Data\logs.dat (15 bytes)
   C:\dir\install\install\server.exe (7547 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (268 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