BKDR_SUB7.22A
Backdoor:Win32/Subseven.2_2, Backdoor:Win32/Litmus.AB (Microsoft); BackDoor-Sub7.svr (McAfee); Backdoor.Litmus.203 (Symantec); PAK:UPX, Backdoor.Win32.SubSeven.22.a (Kaspersky); Trojan.Win32.Ircbot!cobra (v) (Sunbelt)
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
106,211 bytes
EXE
Yes
15 Oct 2012
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 the following copies of itself into the affected system:
- %System%\diyihkx.exe
- %System Root%\EXPLORER.EXE
- %System%\apka.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It creates the following folders:
- %Windows%\litmus
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
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
RunDLL30 = "%System%\diyihkx.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\apka
StubPath = "%System%\apka.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
LTM2 = "%Windows%\litmus\ha.exe"
Other System Modifications
This backdoor modifies the following file(s):
- %System%\drivers\etc\services
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
It adds the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\apka
HKEY_LOCAL_MACHINE\Software\Microsoft\
ENC
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
¸â¼¦¨ = "~vd"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
§ßæ = "²¸Ù"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
¸âº¡ = "²¸Ù"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
¸â¼¦£ = "²¸ÙÍ"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
µÏ²¢ = "°ÈÐgj¢¡{Ьi«¢8¨£Ñl¢£ª£{g}§£2°~¤ÒlÒÎx~ªlixÐ0ª¢Î¥©}¤«hi
«Ò5"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
´Ï¯£¢ = "{random characters}"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
ºÞ¹¨ = "~wee¾»»°g}"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ENC
µÏ²¢ = "ÈÃ}°» ȹ§Á²³2©ªÕå×ät²ä«"
Dropping Routine
This backdoor drops the following files:
- temp.exe
- %Windows%\litmus\ha.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
This report is generated via an automated analysis system.
SOLUTION
9.200
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_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
- apka
- In HKEY_LOCAL_MACHINE\Software\Microsoft
- ENC
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
- RunDLL30 = "%System%\diyihkx.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\apka
- StubPath = "%System%\apka.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- LTM2 = "%Windows%\litmus\ha.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- ¸â¼¦¨ = "~vd"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- §ßæ = "²¸Ù"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- ¸âº¡ = "²¸Ù"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- ¸â¼¦£ = "²¸ÙÍ"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- µÏ²¢ = "°ÈÐgj¢¡{Ьi«¢8¨£Ñl¢£ª£{g}§£2°~¤ÒlÒÎx~ªlixÐ0ª¢Î¥©}¤«hi «Ò5"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- ´Ï¯£¢ = "{random characters}"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- ºÞ¹¨ = "~wee¾»»°g}"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ENC
- µÏ²¢ = "ÈÃ}°» ȹ§Á²³2©ªÕå×ät²ä«"
Step 5
Search and delete these components
- temp.exe
- %Windows%\litmus\ha.exe
Step 6
Search and delete this folder
- %Windows%\litmus
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_SUB7.22A. 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 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\services
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