BKDR_TDSS.AJX
PWS:Win32/Zbot.gen!R, PWS:Win32/Zbot.gen!R (Microsoft); MultiDropper-SJ (McAfee); Infostealer.Banker.C (Symantec); Trojan.Win32.Generic!BT (Sunbelt); Win32/Cryptor.dropper (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
84,245 bytes
EXE
Yes
09 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.
Autostart Technique
This backdoor modifies the following registry entries to ensure it automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
userinit = "%System%\userinit.exe,%System%\sdra64.exe,"
(Note: The default value data of the said registry entry is %Windows%\system32\userinit.exe,.)
Other System Modifications
This backdoor deletes the following files:
- %System%\sdra64.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
It adds the following registry keys:
HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\explorer\
{5ECCBACD-C6EF-355D-5A40-82CE4647642B}
It adds the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
{3039636B-5F3D-6C64-6675-696870667265} = "{random values}"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
{33373039-3132-3864-6B30-303233343434} = "{random values}"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{5ECCBACD-C6EF-355D-5A40-82CE4647642B}
{3039636B-5F3D-6C64-6675-696870667265} = "{random values}"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
{5ECCBACD-C6EF-355D-5A40-82CE4647642B}
{33373039-3132-3864-6B30-303233343434} = "{random values}"
Dropping Routine
This backdoor drops the following files:
- %User Temp%\qLM6SvDcHU.exe
- %System%\sdra64.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% is the Windows system folder, which is usually C:\Windows\System32.)
Other Details
This backdoor connects to the following possibly malicious URL:
- http://{BLOCKED}eam.cn/m1lan0/jAoz46kvgb.bin
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
Identify and delete files detected as BKDR_TDSS.AJX using either the Startup Disk or Recovery Console
Step 3
Delete this registry key
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\microsoft\windows\currentversion\explorer
- {43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
- In HKEY_CURRENT_USER\software\microsoft\windows\currentversion\explorer
- {5ECCBACD-C6EF-355D-5A40-82CE4647642B}
Step 4
Delete this registry value
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\Microsoft\Windows\CurrentVersion\Explorer\{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
- {3039636B-5F3D-6C64-6675-696870667265} = "{random values}"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{43BF8CD1-C5D5-2230-7BB2-98F22C2B7DC6}
- {33373039-3132-3864-6B30-303233343434} = "{random values}"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{5ECCBACD-C6EF-355D-5A40-82CE4647642B}
- {3039636B-5F3D-6C64-6675-696870667265} = "{random values}"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\{5ECCBACD-C6EF-355D-5A40-82CE4647642B}
- {33373039-3132-3864-6B30-303233343434} = "{random values}"
Step 5
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: userinit = "%System%\userinit.exe,%System%\sdra64.exe,"
To: userinit = ""%Windows%\system32\userinit.exe,""
- From: userinit = "%System%\userinit.exe,%System%\sdra64.exe,"
Step 6
Search and delete these components
- %User Temp%\qLM6SvDcHU.exe
- %System%\sdra64.exe
Step 7
Scan your computer with your Trend Micro product to delete files detected as BKDR_TDSS.AJX. 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 8
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.
- %System%\sdra64.exe
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