TROJ_FALSH.A

May 23, 2014
 ALIASES:

TrojanProxy:JS/Cahecon.A (Microsoft); Trojan horse Proxy.BCVI (AVG)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

295,936 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

23 May 2014

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\software\policies\
microsoft\internet explorer\control panel

HKEY_CURRENT_USER\software\policies\
microsoft\internet explorer\control panel

HKEY_CURRENT_USER\Software\Microsoft\
Windows Script\Settings

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
autoconfigurl = "file://%User Temp%\CWS06EX02.txt"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
enablehttpintadura1_1 = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
proxyenable = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
proxyhttpintadura1.1 = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\internet explorer\control panel
advancedtab = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\internet explorer\control panel
resetwebsettings = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\internet explorer\control panel
autoconfig = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
autoconfigurl = "file://%User Temp%\CWS06EX02.txt"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
enablehttpintadura1_1 = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
proxyhttpintadura1.1 = "0"

HKEY_CURRENT_USER\Software\Policies\
Microsoft\internet explorer\control panel
advancedtab = "1"

HKEY_CURRENT_USER\Software\Policies\
Microsoft\internet explorer\control panel
resetwebsettings = "1"

HKEY_CURRENT_USER\Software\Policies\
Microsoft\internet explorer\control panel
autoconfig = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows Script\Settings
JITDebug = "0"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
DisableSR = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
proxyenable = "0"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%.\CWS06EX02.txt
  • %User Temp%\send5734.vbs

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}0.1

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.700

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\software\policies\microsoft\internet explorer
    • control panel
  • In HKEY_CURRENT_USER\software\policies\microsoft\internet explorer
    • control panel
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Script
    • Settings

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • autoconfigurl = "file://%User Temp%\CWS06EX02.txt"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • enablehttpintadura1_1 = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • proxyenable = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • proxyhttpintadura1.1 = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\internet explorer\control panel
    • advancedtab = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\internet explorer\control panel
    • resetwebsettings = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\internet explorer\control panel
    • autoconfig = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • autoconfigurl = "file://%User Temp%\CWS06EX02.txt"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • enablehttpintadura1_1 = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • proxyhttpintadura1.1 = "0"
  • In HKEY_CURRENT_USER\Software\Policies\Microsoft\internet explorer\control panel
    • advancedtab = "1"
  • In HKEY_CURRENT_USER\Software\Policies\Microsoft\internet explorer\control panel
    • resetwebsettings = "1"
  • In HKEY_CURRENT_USER\Software\Policies\Microsoft\internet explorer\control panel
    • autoconfig = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Script\Settings
    • JITDebug = "0"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
    • DisableSR = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • proxyenable = "0"

Step 5

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%.\CWS06EX02.txt
  • %User Temp%\send5734.vbs

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_FALSH.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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