Discovered: June 17, 2005
Updated: February 13, 2007 12:40:51 PM
Type: Virus
Systems Affected: Windows

W32.Tirana is a virus that infects portable executable files with payload and self encryption capabilities.

Antivirus Protection Dates

  • Initial Rapid Release version June 18, 2005
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version June 18, 2005
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date June 22, 2005

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Mircea Ciubotariu

Discovered: June 17, 2005
Updated: February 13, 2007 12:40:51 PM
Type: Virus
Systems Affected: Windows

When W32.Tirana is executed, it performs the following actions:

  1. Takes control through a call instruction injected at the entry point of the program which points to the virus decryption routine, when an infected file is run.

  2. Infects files that meet the following conditions:

    • Unprotected by Windows SFC protection system
    • Must be a valid Win32 PE executable
    • Does not have the presence of the marker "ANIA" (0x41, 0x49, 0x4e, 0x41) at file offset 0x38
    • The last section's end in file must be at least at or over offset 0x1000 (4KB)

  3. Infects a suitable PE file, if found, by adding its code at the end of the executable and modifying 5 bytes from the entry point which will pass control to the viral code when the infected file is executed.

  4. Restores the timestamp of the file to its original state, once the file is infected.

  5. Decrypts itself using one XOR function on dword with variable keys. After that it searches for 0x2c APIs required later, and resolves them using its own sum check import routine.

  6. Hooks any of the compromised computer's imports and modules imports from a predetermined list of 13 to perform some additional actions.

  7. Searches for explorer.exe in the active processes list using its own hashing algorithm and then injects a thread into Explorer's process space.

  8. Searches for .exe files in the current directory and infects those that meet the aforementioned requirements.

  9. Checks for the following mutex in order to avoid reinfection before injecting the thread into Explorer.exe's process space:


When the injected thread is executed, it performs the following actions:

  1. Hooks Explorer's imports and Explorer's modules imports that are in the list of 13 preferred imports.

  2. Creates the mutex "atirania".

  3. Activates the payload if the date is the 11th of July (any year).

    Note: The payload consists of a random movement of the mouse on the screen, with small jumps over very short distances. The frequency of the issued mouse move commands may get as high as 10 per second.

  4. Using the hooked APIs, the virus will be able to infect folders/files when the Explorer process tries to perform different operations, for example GetFileAttributes or SetCurrentDirectory, on them.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Mircea Ciubotariu

Discovered: June 17, 2005
Updated: February 13, 2007 12:40:51 PM
Type: Virus
Systems Affected: Windows

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan and delete all the files detected.
For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

3. To scan for and delete the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected, click Delete.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [File path]
Message body: Windows cannot find [file name]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

Writeup By: Mircea Ciubotariu