- Threat Encyclopedia
- Malware
- WORM_DOWNAD.AC
Worm:Win32/Conficker.B (Microsoft), W32/Conficker.worm (McAfee), Mal/Conficker-C (Sophos)
Windows
Propagates via flashdrives, Copies itself in all available logical drives, Propagates via network shares
This worm arrives via removable drives. It may be dropped by other malware.
It modifies registry entries to disable various system services. This action prevents most of the system functions to be used. It deletes registry entries, causing some applications and programs to not function properly.
It drops copies of itself into all the removable drives connected to an affected system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system. It exploits software vulnerabilities to propagate to other computers across a network.
It uses certain lists of user names and passwords to access password-protected shared files.
It prevents users from visiting antivirus-related websites that contain specific strings.
166,111 bytes
DLL
Yes
05 Apr 2016
Compromises system security, Compromises network security
Arrival Details
This worm arrives via removable drives.
It may arrive via network shares.
It may be dropped by other malware.
Installation
This worm drops the following copies of itself into the affected system:
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %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.)
Autostart Technique
This worm 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\{random characters}
DisplayName = "{random}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Type = "32"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
ErrorControl = "0"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
ObjectName = "Local System"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Description = "{long sentences}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
ImagePath = "%System Root%\system32\svchost.exe -k netsvcs"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}\Parameters
ServiceDll = "%System%\{malware file name}"
It adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters} = "rundll32.exe {malware path and file name}, {Parameter}"
Other System Modifications
This worm adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Applets
dl = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Applets
ds = "0"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets
ds = "0"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets
dl = "0"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters
TcpNumConnections = "0x00FFFFFE" - hex values
(Note: The default value data of the said registry entry is {System Default}.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = "{original value} {random characters}"
(Note: The default value data of the said registry entry is {original value}.)
It modifies registry entries to disable the following system services:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WinDefend
Start = "4"
(Note: The default value data of the said registry entry is 2.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"
(Note: The default value data of the said registry entry is 2.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WerSvc
Start = "4"
(Note: The default value data of the said registry entry is 2.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"
(Note: The default value data of the said registry entry is 2.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "4"
(Note: The default value data of the said registry entry is 2.)
It modifies the following registry entries to hide files with Hidden attributes:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0"
(Note: The default value data of the said registry entry is 1.)
It deletes the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\explorer\
ShellServiceObjects\{FD6905CE-952F-41F1-9A6F-135D9C6622CC}
It deletes the following registry entries:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Defender = "{value}"
Propagation
This worm creates the following folders in all removable drives:
It drops copies of itself into all the removable drives connected to an affected system.
It drops the following copy(ies) of itself in all removable drives:
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
;garbage characters
;garbage characters
shelLExECUte =RuNdLl32.EXE .\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn
;garbage characters
;garbage characters
It exploits the following software vulnerabilities to propagate to other computers across a network:
Information Theft
This worm uses the following lists of user names and passwords to access password-protected shared files:
Other Details
This worm connects to the following URL(s) to get the affected system's IP address:
It connects to the following time servers to determine the current date:
It does the following:
It prevents users from visiting antivirus-related websites that contain the following strings:
9.800
12.448.07
05 Apr 2016
12.449.00
06 Apr 2016
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 WORM_DOWNAD.AC
Step 3
Restart in Safe Mode
Step 4
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.
Step 5
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.
Step 6
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.
Step 7
Search and delete AUTORUN.INF files created by WORM_DOWNAD.AC that contain these strings
Step 8
Search and delete this folder
Step 9
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DOWNAD.AC. 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 10
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.