Worm:Win32/Abfewsm.A is a worm that spreads by placing copies of itself in the folder used for files to be written into CDs. It is capable of modifying a variety of system services as well as disabling Control Panel and registry editors. It may also modify some firewall settings.
Installation
Worm:Win32/Abfewsm.A arrives in the system as a file that uses the Windows Explorer icon. It also creates a shortcut with no icon that points to itself:
- <startup folder>\<no value>.LNK
Note - <startup folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the Startup folder for Windows 9x, Me, NT, 2000, XP and 2003 is '%USERPROFILE%\Start Menu\Programs\Startup'. For Windows Vista, the default location is '%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup'.
Worm:Win32/Abfewsm.A creates compressed file copies of itself in the Windows folder using the following names:
CyberWar.cab
fh_antivirussetup6534.cab
kavSetupEng3857.cab
mario675.cab
New WinRAR archive.cab
New WinRAR ZIP archive.cab
New WinZip File.cab
new-screamsaver.com.cab
supermodels.cab
Youtube.cab
It also copies itself to the following locations:
%windir%\KHATARNAKH.exe
%windir%\Xplorer.exe
%systemroot%\KHATRA.exe
%windir%\system\gHost.exe
<system folder>\KHATRA.exe
Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.
It also creates the following files containing settings it uses:
%windir%\K.Backup\C_Drive_Documents and Settings_Administrator_Start Menu_Programs_Startup_desktop.ini.FUCKED
%windir%\K.Backup\C_Drive_Documents and Settings_All Users_Start Menu_Programs_Startup_desktop.ini.FUCKED
%windir%\K.Backup\C_Drive_Documents and Settings_All Users_Start Menu_Programs_Startup_whoami.lnk.FUCKED
Worm:Win32/Abfewsm.A creates the following registry entries to allow its copy to automatically run every time Windows starts:
Adds value: "PHIME2002A"
With data: "<system folder>\KHATRA.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Adds value: "PHIME2002ASync"
With data: "%windir%\Xplorer.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Adds value: "load"
With data: "<system folder>\KHATRA.exe"
To subkey: HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows
It also creates the following registry key, which contains its settings:
Worm:Win32/Abfewsm.A also creates a job that runs itself every day at 09:00 by running the following commands in succession:
"AT /delete /yes" - deletes all previously scheduled jobs
"AT 09:00 /interactive /EVERY:m,t,w,th,f,s,su C:\WINDOWS\system32\KHATRA.exe" - creates a scheduled task to run its copy
It then adds the following registry entry so that its scheduled job recurs indefinitely:
Adds value: "AtTaskMaxHours"
With data: "0"
To subkey: HKLM\SYSTEM\CurrentControlSet\Services\Schedule
Spreads via…
Compact discs
Worm:Win32/Abfewsm.A copies itself as the following files to ensure that they are included when a CD is written to:
%AppData%\Microsoft\CD Burning\Administrator.exe
%AppData%\Microsoft\CD Burning\KHATRA.exe
%AppData%\Microsoft\CD Burning\New Folder(3).exe - copied as a hidden file
%AppData%\Microsoft\CD Burning\autorun.inf - initialization file that ensures that 'KHATRA.exe' is automatically executed when the CD is accessed and Autorun is enabled
As such, when a CD is written with the affected computer and then run from another computer, the worm copy automatically runs and infects that system.
Payload
Modifies system services
Worm:Win32/Abfewsm.A sets the following services to run automatically:
Remote Desktop Sharing service
Removable Storage service
Remote Desktop Help Session Manager
Terminal Server service
Telnet Server service
UPnP device hosting
It does this by modifying the system registry, respectively:
Adds value: "Start"
With data: "2"
To subkeys:
HKLM\SYSTEM\ControlSet001\Services\mnmsrvc
HKLM\SYSTEM\ControlSet001\Services\NtmsSvc
HKLM\SYSTEM\ControlSet001\Services\RDSessMgr
HKLM\SYSTEM\ControlSet001\Services\TermService
HKLM\SYSTEM\ControlSet001\Services\TlntSvr
HKLM\SYSTEM\ControlSet001\Services\upnphost
Worm:Win32/Abfewsm.A disables the following services:
Protected Storage service
Windows Security Center service
It does this by modifying the system registry, respectively:
Adds value: "Start"
With data: "4"
To subkeys:
HKLM\SYSTEM\ControlSet001\Services\ProtectedStorage
HKLM\SYSTEM\ControlSet001\Services\wscsvc
It also sets the Schedule service to run manually:
Adds value: "Start"
With data: "3"
To subkey: HKLM\SYSTEM\ControlSet001\Services\Schedule
Changes system firewall policy
Worm:Win32/Abfewsm.A modifies the following registry entry, which prevents the system firewall from working:
Modifies value: "Epoch"
From data: "6A, 60, 00, 00"
To data: "6B, 60, 00, 00"
In subkey: HKLM\SYSTEM\ControlSet001\Services\SharedAccess\Epoch
It also modifies the firewall policy so that its copy is tagged as an authorized application and able to pass through the firewall:
Adds value: "<system folder>\KHATRA.exe"
With data: "<system folder>\KHATRA.exe:*:Enabled:System"
To subkey: HKLM\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
Modifies system settings
Worm:Win32/Abfewsm.A disables the option in Windows Explorer to show all files:
Adds value: "CheckedValue"
With data: "0"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
It also enables certain files to be tagged as 'hidden':
Adds value: "Hidden"
With data: "0"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
Worm:Win32/Abfewsm.A also disables the Control Panel and the registry editor tools by modifying the following registry entries:
Modifies value: "NoControlPanel"
With data: "1"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Modifies value: "DisableRegistryTools"
With data: "1"
To subkey: HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System
Modifies Internet Explorer settings
Worm:Win32/Abfewsm.A changes the window title for Internet Explorer to "Internet Exploiter".
Analysis by Jaime Wong