Threat Descriptons



Category :


Type :


Aliases :

Worm.Vbs.HeadTail.a, Virus:VBS/Invadesys.A (Microsoft), VBS.Invadesys.A (Symantec), VBS/HeadTail-A (Sophos)


A standalone malicious program which uses computer or network resources to make complete copies of itself.


Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

UPDATE (July 22 2009):

F-Secure Anti-Virus products had a brief False Alarm with this detection. A clean file called avh_fsav_800_bin was detected as being infected on 21 July 2009. This has now been fixed with the database update, 2009-07-21_10.If the avh_fsav_800_bin file was removed, it will be recreated automatically and there is no need for further action by the user. We apologize for any inconvenience.

Technical Description

Worm:VBS/HeadTail.A is a Visual Basic Script worm that propagates by copying itself to available removable, fixed, and remote drives. It is also able to delete predefined files and processes.


Whenever the specified drive is accessed in systems with Drive Type Autorun Enabled settings, the malware will automatically execute itself.Upon execution, this malware will search in removable, fixed, and remote drives for HTA, HTM, HTML, ASP and VBS files whose file size is less than 350000 Bytes to infect. It then creates a autorun registry entry in :

  • HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows\Load

As a way to infect more files and enable additional executions, the worm modifies the file association of the following file types to execute the malware first:

  • .CHM
  • .HLP
  • .REG
  • .TXT

As part of the malware's restrictions in terms of infection, the malware will infect no more than 1000 files that is found on single execution.HeadTail.A uses the System and Hidden file properties and sets the registry to disable viewing of files with such attributes in order to hide from the user.


HeadTail.A checks the filename and if it contains predefined strings (supposedly related to adult videos), it will delete the file. The file formats are as below:

  • .AVI
  • .MPG
  • .RM
  • .RMVB

It will also monitor and ensure that the following processes are terminated :

  • 360tray.exe
  • cmd.exe
  • msconfig.exe
  • ras.exe
  • regedit.exe
  • regedit.pif
  • regedit.scr
  • SREng.exe
  • taskmgr.exe
  • USBAntiVir.exe

Based on the parameters, HeadTail.A is capable of removing all system modifications and deleting all its copies. It can also disinfect all infected files accessible in the system.

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