BKDR_BIFROST.AT
DDoS:Win32/Nitol.A (Microsoft); Backdoor.Trojan (Symantec); Trojan.Win32.Writos.ppz (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse SHeur4.BEUQ (AVG)
Windows 2000, Windows XP, Windows Server 2003
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
822,945 bytes
EXE
No
29 May 2013
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 creates the following folders:
- %System Root%\DOCUME~1
- %System Root%\DOCUME~1\Wilbert
- %User Profile%\LOCALS~1
- %User Temp%\nsr3.tmp
- %System Root%\drmsoft
- %Program Files%\drmsoft
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %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.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)
Other System Modifications
This backdoor deletes the following files:
- %User Temp%\nsb1.tmp
- %User Temp%\nsr3.tmp
- %System Root%\iexplore2.exe
(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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Shell Folders
Personal = "%User Profile%\My Documents"
(Note: The default value data of the said registry entry is %User Profile%\My Documents.)
Dropping Routine
This backdoor drops the following files:
- %User Temp%\nsr3.tmp\System.dll
- %System Root%\CW_Engine.exe
- %System Root%\iexplore.exe
(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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
This report is generated via an automated analysis system.
SOLUTION
9.300
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
Restore these modified registry values
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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
- From: Personal = "%User Profile%\My Documents"
To: Personal = ""%User Profile%\My Documents""
- From: Personal = "%User Profile%\My Documents"
Step 3
Search and delete these components
- %User Temp%\nsr3.tmp\System.dll
- %System Root%\CW_Engine.exe
- %System Root%\iexplore.exe
Step 4
Search and delete these folders
- %System Root%\DOCUME~1
- %System Root%\DOCUME~1\Wilbert
- %User Profile%\LOCALS~1
- %User Temp%\nsr3.tmp
- %System Root%\drmsoft
- %Program Files%\drmsoft
Step 5
Scan your computer with your Trend Micro product to delete files detected as BKDR_BIFROST.AT. 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.
Step 6
Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %User Temp%\nsb1.tmp
- %User Temp%\nsr3.tmp
- %System Root%\iexplore2.exe
Did this description help? Tell us how we did.