BKDR_NECURS.TS
Trojan:Win32/Necurs.A (Microsoft)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
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 the following copies of itself into the affected system and executes them:
- %Application Data%\{GUID}\syshost.exe - if not logged in as an Administrator
- %Windows%\Installer\{GUID}\syshost.exe - if logged in as an Administrator
(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 and 7.. %Windows% is the Windows folder, which is usually C:\Windows.)
It creates the following folders:
- %Windows%\Installer\{GUID} - if logged in as an Administrator
- %Application Data%\{GUID} - if not logged in as an Administrator
(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %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 and 7.)
Autostart Technique
This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\syshost32
ImagePath = ""%Windows%\Installer\{GUID}\syshost.exe" /service"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\syshost32
ImagePath = ""%Application Data%\{GUID}\syshost.exe" /service"
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\syshost32
Other Details
This backdoor connects to the following possibly malicious URL:
- http://{BLOCKED}.{BLOCKED}.99.237/forum/db.php