Backdoor.Win32.PcClient_0c41ca4dc4

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):

%original file name%.exe:1596
%original file name%.exe:1960
Reader_sl.exe:1064
wuauclt.exe:344
server.exe:868
server.exe:2032
jusched.exe:1056

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

rundll32.exe:608
iexplore.exe:604

File activity

The process %original file name%.exe:1596 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\server.exe (290 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\2222.JPG (24 bytes)

The process %original file name%.exe:1960 makes changes in the file system.

The Backdoor deletes the following file(s):

%Documents and Settings%\%current user%\Local Settings\Temp\~DF9084.tmp (0 bytes)

The process wuauclt.exe:344 makes changes in the file system.

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

%WinDir%\SoftwareDistribution\DataStore\Logs\edb.chk (100 bytes)
%WinDir%\SoftwareDistribution\DataStore\Logs\edb.log (3576 bytes)
%WinDir%\SoftwareDistribution\DataStore\DataStore.edb (100 bytes)

The Backdoor deletes the following file(s):

%WinDir%\SoftwareDistribution\DataStore\Logs\tmp.edb (0 bytes)

The process server.exe:2032 makes changes in the file system.

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

%System%\install\server.exe (1425 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (235 bytes)

The process iexplore.exe:604 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 (2040 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (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 jusched.exe:1056 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\jusched.log (347 bytes)

Registry activity

The process %original file name%.exe:1596 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "61 0F 24 EF 82 0C 91 DA 73 08 58 42 6A 6C AF 60"

[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\ShellNoRoam\MUICache\C:\DOCUME~1\"%CurrentUserName%"\LOCALS~1\Temp]
"server.exe" = "server"

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

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

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 %original file name%.exe:1960 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "27 47 EE C1 24 EE A6 93 C7 D9 97 DB F5 57 1C 99"

The process Reader_sl.exe:1064 makes changes in the system registry.

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

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

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

[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 server.exe:868 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "CB 3A CF 88 BE 3C EC D4 9A 8C CF 6F 0E 57 E8 BE"

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

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

The process server.exe:2032 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "07 29 07 7A 63 37 45 8B 6D 19 7B A6 FD FF 45 C6"

[HKLM\SOFTWARE\Microsoft\Active Setup\Installed Components\{08B0E5JF-4FCB-11CF-AAA5-00401C6XX500}]
"StubPath" = "%System%\install\server.exe Restart"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run]
"Policies" = "%System%\install\server.exe"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run]
"Policies" = "%System%\install\server.exe"

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]
"HKCU" = "%System%\install\server.exe"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"HKLM" = "%System%\install\server.exe"

The process rundll32.exe:608 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "8F DD A0 64 44 AE 00 49 39 A0 14 23 86 1A 29 01"

[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:604 makes changes in the system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "62 5B 50 0E 9C C9 BB F9 05 BA CF C8 6E FB 15 1F"

[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\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\ShellNoRoam\MUICache\%System%\install]
"server.exe" = "server"

[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" = "17/01/2014 -- 07:19"

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"

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):

   %original file name%.exe:1596
   %original file name%.exe:1960
   wuauclt.exe:344
   server.exe:868
   server.exe:2032
   

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\server.exe (290 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\2222.JPG (24 bytes)
   %WinDir%\SoftwareDistribution\DataStore\Logs\edb.chk (100 bytes)
   %WinDir%\SoftwareDistribution\DataStore\Logs\edb.log (3576 bytes)
   %WinDir%\SoftwareDistribution\DataStore\DataStore.edb (100 bytes)
   %System%\install\server.exe (1425 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XX--XX--XX.txt (235 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\XxX.xXx (2040 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\UuU.uUu (32 bytes)
   %Documents and Settings%\%current user%\Application Data\logs.dat (15 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\jusched.log (347 bytes)

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

   [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   "HKCU" = "%System%\install\server.exe"
   
   [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
   "HKLM" = "%System%\install\server.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