Backdoor.Win32.Fynloski_c8cb626e81

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):

msdcsc.exe:1252
attrib.exe:1256
attrib.exe:1280
dwwin.exe:1940
notepad.exe:1568
c8cb626e812d9aa9c482bd4fdb33233e.exe:548
c8cb626e812d9aa9c482bd4fdb33233e.exe:576
reg.exe:336
reg.exe:420
reg.exe:628
reg.exe:448

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

msdcsc.exe:484
msdcsc.exe:1056
notepad.exe:1728
Javascript.exe:1792

File activity

The process msdcsc.exe:484 makes changes in a file system.

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

%Documents and Settings%\%current user%\Local Settings\Temp\5a24_appcompat.txt (3447 bytes)

The process dwwin.exe:1940 makes changes in a file system.

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

%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\desktop.ini (67 bytes)
%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\WH2VKX2N\desktop.ini (67 bytes)
%Documents and Settings%\%current user%\Local Settings\Temp\96B02.dmp (56093 bytes)
%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\TGYVF1DX\desktop.ini (67 bytes)
%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\QALB3X7H\desktop.ini (67 bytes)
%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\6UJDDQ19\desktop.ini (67 bytes)

The process notepad.exe:1568 makes changes in a file system.

The Backdoor deletes the following file(s):

C:\c8cb626e812d9aa9c482bd4fdb33233e.exe (0 bytes)

The process Javascript.exe:1792 makes changes in a file system.

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

%Documents and Settings%\%current user%\Application Data\Javascript.exe (161 bytes)
%Documents and Settings%\%current user%\Application Data\JVB (33 bytes)

The process c8cb626e812d9aa9c482bd4fdb33233e.exe:548 makes changes in a file system.

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

%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe (7547 bytes)

The process c8cb626e812d9aa9c482bd4fdb33233e.exe:576 makes changes in a file system.

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

%Documents and Settings%\%current user%\Local Settings\Temp\Javascript.exe (628 bytes)

Registry activity

The process msdcsc.exe:484 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "83 74 B4 F3 DE 9D 39 40 90 7E EE 08 9C DC 3F E4"

The Backdoor deletes the following registry key(s):

[HKLM\SOFTWARE\Microsoft\PCHealth\ErrorReporting\DW]

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

[HKLM\SOFTWARE\Microsoft\PCHealth\ErrorReporting\DW]
"DWFileTreeRoot"

The process msdcsc.exe:1056 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "EB 71 B5 69 64 D3 95 FF 68 88 6A 20 2F 0D E5 26"

[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\Shell Folders]
"AppData" = "%Documents and Settings%\%current user%\Application Data"

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

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]
"MicroUpdate" = "%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe"

The process attrib.exe:1256 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "28 1D F8 36 45 86 8D 99 97 4F 9E 84 5B EB 09 0F"

The process attrib.exe:1280 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "4E 75 31 05 5E 99 15 6D F1 44 FB 2B B1 F5 7D DA"

The process dwwin.exe:1940 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "8E 34 B6 5D F8 21 C5 6D 59 D9 6F BA 23 93 4B 57"

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

[HKLM\System\CurrentControlSet\Hardware Profiles\0001\Software\Microsoft\windows\CurrentVersion\Internet Settings]
"ProxyEnable" = "0"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path2]
"CachePath" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\Cache2"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path1]
"CachePath" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\Cache1"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path3]
"CacheLimit" = "65452"

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

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path1]
"CacheLimit" = "65452"

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

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths]
"Directory" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5"

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

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path4]
"CacheLimit" = "65452"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path4]
"CachePath" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\Cache4"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path3]
"CachePath" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\Cache3"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths]
"Paths" = "4"

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

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Connections]
"SavedLegacySettings" = "3C 00 00 00 14 00 00 00 01 00 00 00 00 00 00 00"

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

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path2]
"CacheLimit" = "65452"

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

Proxy settings are disabled:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"ProxyEnable" = "0"

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

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"AutoConfigURL"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"ProxyServer"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"ProxyOverride"

The process notepad.exe:1568 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "21 47 83 4E 21 29 8D 11 7F D4 E0 62 43 49 0A E5"

The process notepad.exe:1728 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "9F 89 1A 90 BC 2F 9B 3F E8 B6 80 4D 4C 75 26 7A"

The process Javascript.exe:1792 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "89 93 F6 92 51 02 A3 A6 8F 92 E5 8C 43 1F C9 B5"

[HKLM\SOFTWARE\Microsoft\Active Setup\Installed Components\{FF1BBCCD-05CB-CFAE-EFC3-E83A7AA1BDCE}]
"StubPath" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"

[HKCU\Software\VB and VBA Program Settings\INSTALL\DATE]
"67WJPNBV2T" = "August 22, 2013"

[HKCU\Software\VB and VBA Program Settings\SrvID\ID]
"67WJPNBV2T" = "Anonymous's Bot"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\run]
"Windows Defender" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"

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

[HKCU\Software\Microsoft\Active Setup\Installed Components\{FF1BBCCD-05CB-CFAE-EFC3-E83A7AA1BDCE}]
"StubPath" = "%Documents and Settings%\%current user%\Application Data\Javascript.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:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"Windows Defender" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"Windows Defender" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"

The process c8cb626e812d9aa9c482bd4fdb33233e.exe:548 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "3D 9C 28 FA 2A A4 96 7F 86 8F 09 A0 D1 EA 67 DB"

[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"

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

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

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd75-744b-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]
"Personal" = "%Documents and Settings%\%current user%\My Documents"

[HKCU\Software\Microsoft\Windows\ShellNoRoam\MUICache\%Documents and Settings%\%current user%\My Documents\MSDCSC]
"msdcsc.exe" = "msdcsc"

The Backdoor adds the reference to itself to be executed when a user logs on:

[HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"UserInit" = "%System%\userinit.exe,%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.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]
"MicroUpdate" = "%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe"

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:

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

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 process c8cb626e812d9aa9c482bd4fdb33233e.exe:576 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "18 B5 D4 DF DF 2E 60 A4 82 5E A0 2A 07 DC DF 87"

[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"

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

[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:

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

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 process reg.exe:336 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "49 5A 43 6A 69 23 C2 34 C6 D4 56 E5 D9 AC D6 43"

Adds a rule to the firewall Windows which allows any network activity:

[HKLM\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List\%Documents and Settings%\%current user%\Application Data]
"Javascript.exe" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe:*:Enabled:Windows Messanger"

The process reg.exe:420 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "6F DD 9C 28 0B 60 32 CA A0 4F 7B 79 2A D5 34 42"

[HKLM\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile]
"DoNotAllowExceptions" = "0"

The process reg.exe:628 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "25 C3 F1 23 BA 0A 88 B0 EE FF 3C 4A 09 9E 94 E2"

Adds a rule to the firewall Windows which allows any network activity:

[HKLM\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List\C:\DOCUME~1\"%CurrentUserName%"\LOCALS~1\Temp]
"Javascript.exe" = "C:\DOCUME~1\"%CurrentUserName%"\LOCALS~1\Temp\Javascript.exe:*:Enabled:Windows Messanger"

The process reg.exe:448 makes changes in a system registry.

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

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "78 53 CE F6 9C 9E E0 5B 5B 51 83 1E D0 D3 18 E0"

[HKLM\System\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile]
"DoNotAllowExceptions" = "0"

Network activity (URLs)

No activity has 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):

   msdcsc.exe:1252
   attrib.exe:1256
   attrib.exe:1280
   dwwin.exe:1940
   notepad.exe:1568
   c8cb626e812d9aa9c482bd4fdb33233e.exe:548
   c8cb626e812d9aa9c482bd4fdb33233e.exe:576
   reg.exe:336
   reg.exe:420
   reg.exe:628
   reg.exe:448

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\5a24_appcompat.txt (3447 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\desktop.ini (67 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\WH2VKX2N\desktop.ini (67 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\96B02.dmp (56093 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\TGYVF1DX\desktop.ini (67 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\QALB3X7H\desktop.ini (67 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temporary Internet Files\Content.IE5\6UJDDQ19\desktop.ini (67 bytes)
   %Documents and Settings%\%current user%\Application Data\Javascript.exe (161 bytes)
   %Documents and Settings%\%current user%\Application Data\JVB (33 bytes)
   %Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe (7547 bytes)
   %Documents and Settings%\%current user%\Local Settings\Temp\Javascript.exe (628 bytes)

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

   [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   "MicroUpdate" = "%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe"
   
   [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
   "Windows Defender" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"
   
   [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   "Windows Defender" = "%Documents and Settings%\%current user%\Application Data\Javascript.exe"
   
   

5. Remove the references to the Backdoor by modifying the following registry value(s) (How to Work with System Registry):

   [HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
   "UserInit" = "%System%\userinit.exe,%Documents and Settings%\%current user%\My Documents\MSDCSC\msdcsc.exe"

6. Find and delete all copies of the worm's file together with "autorun.inf" scripts on removable drives.
   
7. 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