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Virus Encyclopedia

Welcome to the Virus Encyclopedia of Panda Security.


Threat LevelSevere threatDamageSevereDistributionModerately widespread
Common name:ButterflyBot.A
Technical name:W32/ButterflyBot.A.worm
Threat level:Severe

It is a bot worm, whose main purpose is to allow its creator to use the computer as a zombie, so that it can receive instructions without user’s awareness. Some of the commands it can receive are: to download and run malware in the computer and to update the bot. It spreads through removable drives, via MSN Messenger and P2P programs.

Affected platforms:

Windows 2003/XP/2000/NT/ME/98/95; Other

First detected on:Feb. 3, 2010
Detection updated on:April 14, 2010

Brief Description 


ButterflyBot.A is bot worm whose aim is to make the affected computer become a zombie, so that it can be remotely controlled and receive instructions without either the consent and knowledge of the user.

Some of the instructions that it can receive are to download and run any file in the compromised computer. This implies an important risk for the security of the computer, as any malware can be installed in the computer.

Other commands that it can receive is to download updates of the bot, which can include new functionalities and make its detection more difficult.

One of the strong points of this bot is that it uses several means of propagation:

  • It makes copies of itself in the removable drives connected to the computer, like USB keys.
  • It sends instant messages via MSN Messenger with a link that points to the download of the bot.
  • It makes copies of itself in the shared folders of several P2P programs, using the names of legitimate applications, so that other users download them thinking they are inoffensive files.

Visible Symptoms 


Its main purpose is to be installed in the computer and allow its creator to use it as a zombie. For this reason, the user will not notice any evidence of the actions carried out by the bot, which are detailed in the "Technical details" section.

ButterflyBot.A is specifically designed to avoid being detected. That’s why the user will not appreciate any symptom of the infection.