Analysis by: Mark Joseph Manahan
ALIASES:

Trojan horse Generic21.MMG (AVG) ,W32/Buzus.GA!tr (Fortinet) ,W32/StartPage.AU.gen!Eldorado (generic, not disinfectable) (Fprot) ,Trojan.Win32.Buzus (Ikarus) ,Trojan.Win32.Buzus.gwud (Kaspersky) ,Backdoor:Win32/Bifrose.HZ (Microsoft) ,a variant of Win32/Injector.EWT trojan (Eset) ,Trojan.Gen (Symantec) ,Bck/Bifrost.gen (Panda) ,Trojan.Win32.Buzus.gwud (v) (Sunbelt)

 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:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor 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: 374,997 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Jan 2014

Arrival Details

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

Installation

This backdoor adds the following folders:

  • %System%\Bifrost

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops the following files:

  • %System%\Bifrost\logg.dat
  • %System Root%\www.google.com.htm

It drops the following copies of itself into the affected system:

  • %System%\Bifrost\server.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{25AC4F9D-0ADD-F7A0-6484-13AADF8ECE71}
stubpath = "%System%\Bifrost\server.exe s"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Bifrost

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes

HKEY_LOCAL_MACHINE\Software\Bifrost

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{25AC4F9D-0ADD-F7A0-6484-13AADF8ECE71}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Bifrost
klg = "01"

HKEY_LOCAL_MACHINE\Software\Bifrost
nck = "{Hex Values}"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes
DownloadUpdates = "0x00023c00"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes
DisplayName = "Google"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes
URL = "http://www.google.com/cse?cx=partner-pub-9588033570232632:rhmyra-cwbb&q={searchTerms}"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes
SuggestionsURLFallback = "http://www.google.com/cse?cx=partner-pub-9588033570232632:rhmyra-cwbb&q={searchTerms}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • q33q.no-ip.biz

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.562.03
FIRST VSAPI PATTERN DATE: 25 Jan 2014
VSAPI OPR PATTERN File: 10.563.00
VSAPI OPR PATTERN Date: 25 Jan 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_CURRENT_USER\Software
    • Bifrost
  • In HKEY_CURRENT_USER\Software\Microsoft
    • Internet Explorer\SearchScopes
  • In HKEY_LOCAL_MACHINE\Software
    • Bifrost
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
    • {25AC4F9D-0ADD-F7A0-6484-13AADF8ECE71}

Step 4

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.

Step 5

Search and delete these files

[ Learn More ]
There may be some files 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. DATA_GENERIC
Note: To do a search for the following files, right-click Start then click Search... or Find..., depending on the version of Windows you are running. For each file to be deleted, type its file name in the Named input box. In the Look In drop-down list, select My Computer, then press Enter.
  • Once located, select the file then press SHIFT+DELETE to permanently delete the file.
  • Repeat the said steps for all files listed.

    • Step 6

    Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_BIFROSE.GFS. 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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