Threat Description

Apost

Details

Aliases:Apost, I-Worm.Readme, W32/Apost@mm, Readme, Readme.exe, W32/Apost-A, W95/Urquest.24576, W32.Urgent.Worm@mm, Win32/Yoview.A@mm
Category:Malware
Type:Worm
Platform:W32

Summary



Readme is a simple mass-mailer written in Visual Basic. The worm has been found in the wild on September 3rd, 2001. It is a PE EXE file 24576 bytes long. Its code is not compressed.



Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More

You may wish to refer to the Support Community for further assistance. You also may also refer to General Removal Instructions for a general guide on alternative disinfection actions.



Technical Details



When the worm's file is run it shows a messagebox with one big button labeled 'Open' and 'Urgent' as caption.

After a user clicks 'Open' button, the worm shows a fake error message:

WinZip SelfExtractor: Warning
 CRC error: 234#21

Then the worm checks if it is already installed in a system. It looks for README.EXE file in \Windows\ folder and creates it if it's not there. The worm then modifies the Registry - it adds 'macrosoft' subkey to the current user's application autostartup key:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]

The 'macrosoft' subkey contains a full path for the worm's file. For example if Windows is installed with default settings, the subkey value will be 'c:\windows\readme.exe'. This way the worm starts every time when Windows is loaded.

The worm also copies itself as README.EXE to root directories of all drives that are available for writing (local and network drives where current user has write access).

Finally the worm connects to Microsoft Outlook, gets user's mail server login and password and sends itself to all e-mail addresses found in Outlook's address book. The infected message looks like that:

Subject: As per your request!
  Body: Please find attached file for your review.
  I look forward to hear from you again very soon.
  Thank you.
  Attachment: Readme.exe

The worm's file is attached to an infected message as README.EXE file. It will infect a remote computer only when a recepient runs the attachment.

Infected messages are deleted after they are sent.

Instructions for manual removing: To remove this worm from a system it's enough to delete its file (README.EXE) from \Windows\ folder and from root directories of all drives that an infected computer has access to. If the worm's file is locked, it is advised to delete it from pure DOS or in case of Windows NT/2000 rename the file with a non-executable extension, reboot a system and then delete the previously renamed worm's file.

F-Secure Anti-Virus detects Apost worm with the updates available here:

http://www.europe.f-secure.com/download-purchase/updates.shtml





Technical Details: Alexey Podrezov, Katrin Tocheva; F-Secure Corp.; September 3, 2001


SUBMIT A SAMPLE

Suspect a file or URL was wrongly detected? Submit a sample to our Labs for analysis

Submit Now

Give And Get Advice

Give advice. Get advice. Share the knowledge on our free discussion forum.

Learn More