Backdoor.Win32.RECSLURP.A
HEUR:Trojan.Win32.Generic (Kaspersky); TrojanDownloader:Win32/Recslurp.A (Microsoft)
Windows
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
Downloaded from the Internet
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 executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.
TECHNICAL DETAILS
143,494 bytes
EXE
Yes
25 Apr 2019
Connects to URLs/IPs
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 and executes the following files:
- %Application Data%\csrss.exe
- %Application Data%\rundll32.exe
- %Application Data%\svchost.exe
or - %Application Data%\System32\csrss.exe
- %Application Data%\System32\rundll32.exe
- %Application Data%\System32\svchost.exe
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)
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
Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Service Host Process for Windows = "%Application Data%\svchost.exe" or "%Application Data%\System32\svchost.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Host-process Windows (Rundll32.exe) = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
Other System Modifications
This Backdoor adds the following registry keys:
HKEY_CURRENT_USER\SOFTWARE\BC Clients
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
HKEY_CURRENT_USER\Software\BC Clients
{random character} = {encrypted data}
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
Backdoor Routine
This Backdoor executes the following commands from a remote malicious user:
- Download and execute a file
- Sleep command
- Modify registry entries
- Gather system information
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- {BLOCKED}klo.net
- {BLOCKED}.{BLOCKED}.3.184
However, as of this writing, the said sites are inaccessible.
Other Details
This Backdoor connects to the following URL(s) to check for an Internet connection:
- smtp.live.com
- smtp.mail.ru
SOLUTION
9.850
14.962.04
26 Apr 2019
14.963.00
27 Apr 2019
Step 1
Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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
- Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
- Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Service Host Process for Windows = "%Application Data%\svchost.exe" or "%Application Data%\System32\svchost.exe"
- Service Host Process for Windows = "%Application Data%\svchost.exe" or "%Application Data%\System32\svchost.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Host-process Windows (Rundll32.exe) = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- Host-process Windows (Rundll32.exe) = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- Client Server Runtime Process = "%Application Data%\csrss.exe" or "%Application Data%\System32\csrss.exe"
- In HKEY_CURRENT_USER\Software\BC Clients
- {random character} = "{encrypted data}"
- {random character} = "{encrypted data}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
- Host-process Windows (Rundll32.exe) = "%Application Data%\rundll32.exe" or "%Application Data%\System32\rundll32.exe"
Step 5
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
- BC Clients
- BC Clients
Step 6
Search and delete this file
- %Application Data%\csrss.exe
- %Application Data%\rundll32.exe
- %Application Data%\svchost.exe
- %Application Data%\System32\csrss.exe
- %Application Data%\System32\rundll32.exe
- %Application Data%\System32\svchost.exe
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.RECSLURP.A. 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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