Backdoor.Win32.PcClient_79a39e38fd

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):

ctfmon.exe:252
server.exe:2264
vbc.exe:2532

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

rundll32.exe:2292
%original file name%.exe:2420
vbc.exe:4020

File activity

The process vbc.exe:2532 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 (319 bytes)

The process vbc.exe:4020 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 (5128 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (56 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\1546003_10202900102852836_1834368544_n.jpg (83 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)

Registry activity

The process ctfmon.exe:252 makes changes in the system registry.

The Backdoor deletes the following value(s) in system registry:

The Backdoor disables automatic startup of the application by deleting the following autorun value:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"internat.exe"

The process server.exe:2264 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "3C D1 77 BB 27 C7 EA FD 8F F7 17 83 70 C9 A6 0A"

The process rundll32.exe:2292 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "87 B3 D9 24 49 EE 80 8B FA 91 09 B7 12 7E D4 81"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{773a730e-74fb-11e2-b597-000c293bdf2f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f3-7454-11e2-b4cd-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f5-7454-11e2-b4cd-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f2-7454-11e2-b4cd-806d6172696f}]
"BaseClass" = "Drive"

The process %original file name%.exe:2420 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "1D 6F B5 2E C3 A9 95 D4 79 D5 FB 5F 1A 72 68 73"

[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 vbc.exe:2532 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "D1 B1 61 E6 D9 9B 46 BD D9 F4 9F D0 57 73 21 B1"

[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\{3X8260X1-7NA6-2W15-VS47-X7M43SPVN753}]
"StubPath" = "c:\dir\install\install\server.exe Restart"

The process vbc.exe:4020 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "FB E7 58 C4 66 1C 41 F5 BB 92 6A 82 A3 AA CA 4D"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f3-7454-11e2-b4cd-806d6172696f}]
"BaseClass" = "Drive"

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

[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"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{773a730e-74fb-11e2-b597-000c293bdf2f}]
"BaseClass" = "Drive"

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

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f2-7454-11e2-b4cd-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{fdd9f6f5-7454-11e2-b4cd-806d6172696f}]
"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\Shell Folders]
"Cookies" = "%Documents and Settings%\%current user%\Cookies"

[HKCU\Software\vítima]
"NewIdentification" = "vítima"
"FirstExecution" = "19/01/2014 -- 00:36"

[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 web-nodes that bypassing proxy to the Intranet Zone:

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

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

"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"

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:2264
   vbc.exe:2532
   

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

   C:\dir\install\install\server.exe (7547 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (319 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XxX.xXx (5128 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (56 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\1546003_10202900102852836_1834368544_n.jpg (83 bytes)
   %Documents and Settings%\%current user%\Application Data\logs.dat (15 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