BKDR_ZACCESS.SA
Trojan:Win32/Sirefef.P (Microsoft), ZeroAccess.hr (McAfee), Backdoor.Win32.ZAccess.bdqj (Kaspersky), Troj/ZAccess-HJ (Sophos)
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:
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 files:
- %System Root%\RECYCLER\S-1-18\${random}\@
- %System Root%\RECYCLER\S-1-18\${random}\n
- %System Root%\RECYCLER\S-1-18\${random}\U\{random}.$
- %System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\@
- %System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\n
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It creates the following folders:
- %System Root%\RECYCLER\S-1-18\${random}\U
- %System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\U
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Classes\
CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InprocServer32
{Default} = "%System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\n."
It modifies the following registry entry(ies) to enable its automatic execution at every system startup:
HKEY_CLASSES_ROOT\CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\
InprocServer32
{Default} = "%System Root%\RECYCLER\S-1-18\${random}\n."
(Note: The default value data of the said registry entry is "%System%\wbem\fastprox.dll".)
Other System Modifications
This backdoor modifies the following registry entries:
HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\
InProcServer32
ThreadingModel = "Both"
(Note: The default value data of the said registry entry is "Apartment".)
It deletes the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WSCSVC
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WUAUSERV
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SHAREDACCESS
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Other Details
This backdoor connects to the following possibly malicious URL:
- http://j.{BLOCKED}nd.com/app/geoip.js
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
Scan your computer with your Trend Micro product and note files detected as BKDR_ZACCESS.SA
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\Classes\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InprocServer32
- {Default} = "%System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\n."
- {Default} = "%System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}\n."
Step 5
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InProcServer32
- From: ThreadingModel = "Both"
To: ThreadingModel = "Apartment"
- From: ThreadingModel = "Both"
- In HKEY_CLASSES_ROOT\CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\InprocServer32
- From: {Default} = "%System Root%\RECYCLER\S-1-18\${random}\n."
To: {Default} = "%System%\wbem\fastprox.dll"
- From: {Default} = "%System Root%\RECYCLER\S-1-18\${random}\n."
Step 6
Search and delete these folders
- %System Root%\RECYCLER\S-1-18\${random}
- %System Root%\RECYCLER\S-1-5-21-1614895754-436374069-682003330-1003\${random}
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZACCESS.SA. 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 8
Restore these deleted registry keys/values from backup
*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
- LEGACY_WSCSVC
- LEGACY_WSCSVC
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- wscsvc
- wscsvc
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
- LEGACY_WUAUSERV
- LEGACY_WUAUSERV
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- wuauserv
- wuauserv
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
- LEGACY_SHAREDACCESS
- LEGACY_SHAREDACCESS
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- SharedAccess
- SharedAccess
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- BITS
- BITS
Did this description help? Tell us how we did.