BKDR_ANDROM.YUYDS
Trojan:Win32/Skeeyah.A!bit (Microsoft); RDN/Generic BackDoor (McAfee); Backdoor.Win32.Androm.hkxi (Kaspersky); Mal/EncPk-CK (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Inject2.CLNV (AVG)
Windows
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
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:
- %User Temp%\62781
- %User Temp%\62781\....
- %User Temp%\62796
- %User Temp%\62796\....
- %User Temp%\AA_
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
S20s28Us = "{malware path and file name}"
Other System Modifications
This backdoor modifies the following file(s):
- %System%\drivers\etc\hosts
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
It deletes the following files:
- %User Temp%\62781\TemporaryFile\TemporaryFile
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)
It deletes the following folders:
- %User Temp%\62781\TemporaryFile
- %User Temp%\62796\TemporaryFile
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)
It adds the following registry keys:
HKEY_CURRENT_USER\Software\Microsoft\
Windows Script\Settings
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\attrib.exe = "%System%\attrib.exe:*:Enabled:Sevsl"
HKEY_CURRENT_USER\Software\Microsoft\
Windows Script\Settings
JITDebug = "0"
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "www.naver.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome.)
Dropping Routine
This backdoor drops the following files:
- %System%\drivers\etc\hosts.ics
- %User Temp%\58b8052567ade6540adf05ec8d813970.zip
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)
Other Details
This backdoor connects to the following possibly malicious URL:
- {BLOCKED}0.1
- {BLOCKED}.8.88
- {BLOCKED}.92.152
- {BLOCKED}.156.196
This report is generated via an automated analysis system.
SOLUTION
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
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 Script
- Settings
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- S20s28Us = "{malware path and file name}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- %System%\attrib.exe = "%System%\attrib.exe:*:Enabled:Sevsl"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows Script\Settings
- JITDebug = "0"
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_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- From: Start Page = "www.naver.com"
To: Start Page = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome""
- From: Start Page = "www.naver.com"
Step 6
Search and delete these components
- %System%\drivers\etc\hosts.ics
- %User Temp%\58b8052567ade6540adf05ec8d813970.zip
Step 7
Search and delete these folders
- %User Temp%\62781
- %User Temp%\62781\....
- %User Temp%\62796
- %User Temp%\62796\....
- %User Temp%\AA_
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ANDROM.YUYDS. 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 9
Restore deleted/modified files and/or registry entries from backup
*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- %System%\drivers\etc\hosts
Step 10
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%\62781\TemporaryFile\TemporaryFile
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