BKDR_PUDSHELL.B
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
Downloaded from the Internet, Dropped by other malware
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
124,928 bytes
EXE
Yes
10 Apr 2014
Compromises system security, 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 the following non-malicious file:
- %System%\c_130475.NLS
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- {MSC.W1758F-AA438F129C.CFF}
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000\Control
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Security
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Enum
It adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR
NextInstance = "1"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
Service = "SRMsvr"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
Legacy = "1"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
ConfigFlags = "0"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
Class = "LegacyDriver"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
ClassGUID = "{8ECC055D-047F-11D1-A537-0000F8753ED1}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000
DeviceDesc = "Security Object Audit"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000\Control
*NewlyCreated* = "0"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SRMSVR\
0000\Control
ActiveService = "SRMsvr"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
Type = "10"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
ImagePath = "{malware path}\{malware name}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
DisplayName = "Security Object Audit"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr
Description = "Responsible for performing security access checks on objects, manipulating privileges (user rights), and generating any resulting security audit messages."
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Security
Security = "{values}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Enum
0 = "Root\Legacy_SRMSVR\0000"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Enum
Count = "1"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SRMsvr\Enum
NextInstance = "1"
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- Remote command prompt
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- http://{BLOCKED}ll.eset-service.com:4624
It posts the following information to its command and control (C&C) server:
- Host name
However, as of this writing, the said sites are inaccessible.
SOLUTION
9.700
10.718.05
10 Apr 2014
10.719.00
11 Apr 2014
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\SYSTEM\CurrentControlSet\Enum\Root
- LEGACY_SRMSVR
- LEGACY_SRMSVR
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- SRMsvr
- SRMsvr
Step 4
Scan your computer with your Trend Micro product to delete files detected as BKDR_PUDSHELL.B. 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 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_PUDSHELL.B. 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.
Did this description help? Tell us how we did.