TROJ_NECURS.USNF
Trojan:Win32/Necurs (Microsoft); RDN/Generic Dropper (McAfee); Trojan.Gen (Symantec); Trojan-Dropper.Win32.Necurs.zdu (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Downloader.Generic14.ADEW (AVG)
Windows
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Trojan 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 Trojan 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 Trojan drops the following copies of itself into the affected system:
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}\syshost.exe
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
It creates the following folders:
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
Other System Modifications
This Trojan deletes the following files:
- {malware path and file name}.tmp
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}\syshost.exe:Zone.Identifier
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}\syshost.exe.tmp
- %User Temp%\157e193d.tmp
(Note: %Windows% is the Windows folder, where it usually is C:\Windows 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.)
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
f259adc725e5da46 = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
68a49afff60febcd = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
1d15213fe659428 = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
5f551a404b4e78da = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\syshost32
3777bf2f6573c1b6 = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
EnableFirewall = "0"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
DoNotAllowExceptions = "0"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = "0"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
DoNotAllowExceptions = "0"
Dropping Routine
This Trojan drops the following files:
- %Temp%\a6b5518b-97a3-f0e0-8be5-5e1f98b174b4.tmp
(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)
Other Details
This Trojan connects to the following possibly malicious URL:
- {BLOCKED}0.188.221
- {BLOCKED}2.252.152
- {BLOCKED}5.65.71
- {BLOCKED}8.163.93
- {BLOCKED}.118.223
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
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\SYSTEM\ControlSet001\Services\syshost32
- f259adc725e5da46 = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
- 68a49afff60febcd = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
- 1d15213fe659428 = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
- 5f551a404b4e78da = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\syshost32
- 3777bf2f6573c1b6 = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile
- EnableFirewall = "0"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile
- DoNotAllowExceptions = "0"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
- EnableFirewall = "0"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
- DoNotAllowExceptions = "0"
Step 3
Search and delete this file
- %Temp%\a6b5518b-97a3-f0e0-8be5-5e1f98b174b4.tmp
Step 4
Search and delete this folder
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}
Step 5
Scan your computer with your Trend Micro product to delete files detected as TROJ_NECURS.USNF. 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 6
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.
- {malware path and file name}.tmp
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}\syshost.exe:Zone.Identifier
- %Windows%\Installer\{8A91C8B0-5D6A-B866-8F10-12536EB044F9}\syshost.exe.tmp
- %User Temp%\157e193d.tmp
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