Email-Worm.Win32.Agent.ev arrives on systems as an e-mail attachment and attempts to download additional components onto the system if executed.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Email-Worm:W32/Agent.EV spreads as an attachment in spam e-mail with attention grabbing lines in the subject field.
The following e-mail subjects have been observed:
- Hot News
- Hot Pictures
- Paris Hilton
- Something Hot
The attachment is named Saver.zip.
When the malware is extracted and executed, it will drop the following components:
%Windir% is the Windows directory. This is usually C:\Windows.[name] is a random filename. Observed examples are Mvd37.sys and Irv31.sys. The contents of the files are the same.WinData.cab is a copy of WinNt32.dll.
All of the dropped components are detected asTrojan-Downloader:W32/Agent.NSL.
The following registry entries are created to load WinNt32.dll on every system startup:
- HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\WinNt32DLLName = WinNt32.dllStartShell = WLEventStartShellImpersonate = 00000000Asynchronous = 00000000ID = 0000003C
The following registry entries are created to start the [name].sys file as a service:
- HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\[name].sys (default) = Driver
- HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\[name].sys (default) = Driver
- HKLM\SYSTEM\CurrentControlSet\Services\[name]Type = 00000001Start = 00000003ErrorControl = 00000000ImagePath = System32\drivers\[name].sys
Similar changes are made in HKLM\SYSTEM\ControlSet001\Services\[name] and HKLM\SYSTEM\ControlSet002\Services\[name].
The Trojan-Downloader:W32/Agent.NSL DLL component will then attempt to connect to one of the following addresses:
Other slightly modified variants may attempt to connect to different addresses.