BKDR_VAWTRAK.YUYIM
Windows
![](/vinfo/imgFiles/legend.jpg)
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.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
188,416 bytes
EXE
No
24 Feb 2016
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 drops a copy of itself in the following folders using different file names:
- %Application Data%\{random folder}\{random filename}
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
Autostart Technique
This backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{10 random numbers} = "%Application Data%\{random folder}\{random filename}"
Other System Modifications
This backdoor adds the following registry keys:
HKCU\Software\{GUID}\
{random folder name}\{4 random numbers}
{random 4 letters} = {hex values}
HKCU\Software\Microsoft\
Internet Explorer\Main
NoProtectedModeBanner = "1"
HKCU\Software\Microsoft\
Internet Explorer\Main
TabProcGrowth = "0"
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
2500 = 3
Other Details
This backdoor deletes the initially executed copy of itself
SOLUTION
9.800
12.330.01
09 Feb 2016
12.331.80
10 Feb 2016
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
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
Step 4
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\Run
- {10 random numbers} = "%Application Data%\{random folder}\{random filename}"
- {10 random numbers} = "%Application Data%\{random folder}\{random filename}"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- NoProtectedModeBanner = 1
- NoProtectedModeBanner = 1
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- TabProcGrowth = 0
- TabProcGrowth = 0
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_VAWTRAK.YUYIM. 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
Reset Internet security settings
Step 7
The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.
- In HKEY_CURRENT_USER\Software\{GUID}\{random folder name}\{4 random numbers}
- {random 4 letters} = {hex values}
- {random 4 letters} = {hex values}
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