BKDR_REMCOS.TICOGBF
Exploit.Win32.BypassUAC.lmq (KASPERSKY), W32/Kryptik.GEAB!tr (FORTINET)
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 drops a copy of itself in the following folders using different file names:
- %Application Data%\Microsoft\csrss.exe (w/ no admin rights)
- %System%\Microsoft\csrss.exe (w/ admin rights)
(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.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
It drops the following files:
- %Application Data%\remcos\logs.dat
(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 adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
Other System Modifications
This Backdoor adds the following registry keys:
HKEY_CURRENT_USER\Software\Qt01lk2A-M2MXUN
It adds the following registry entries as part of its installation routine:
HKEY_CURRENT_USER\Software\Qt01lk2A-M2MXUN
EXEpath = {hex data}
It modifies the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = 0
(Note: The default value data of the said registry entry is 1.)
Other Details
This Backdoor connects to the following possibly malicious URL:
- http://1.{BLOCKED}i.club
- http://{BLOCKED}.{BLOCKED}.106.2
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
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 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\Run
- csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
- csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
- csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
- csrss = "%System%\Microsoft\csrss.exe" (w/ admin rights)
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
- csrss = "%Application Data%\Microsoft\csrss.exe" (w/ no admin rights)
Step 5
Restore this modified 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\Policies\System
- From: EnableLUA = "0"
To: EnableLUA = 1
- From: EnableLUA = "0"
Step 6
Search and delete this file
- %System%\Microsoft\csrss.exe (w/ admin rights)
- %Application Data%\Microsoft\csrss.exe (w/ no admin rights)
- %Application Data%\remcos\logs.dat
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_REMCOS.TICOGBF. 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.
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