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Virus Encyclopedia

Welcome to the Virus Encyclopedia of Panda Security.


Threat LevelHigh threatDamageSevereDistributionNot widespread
Common name:Bagle.O
Technical name:W32/Bagle.O.worm
Threat level:Medium

It infects PE files, creates a backdoor that opens TCP port 2556 and ends processes belonging to security applications. It stops functioning after December 31, 2005.

Affected platforms:

Windows XP/2000/NT/ME/98/95

First detected on:March 15, 2004
Detection updated on:Feb. 18, 2007
Proactive protection:
Yes, using TruPrevent Technologies
Repair utility:Panda QuickRemover

Brief Description 


Bagle.O is a virus that has worm characteristics. Bagle.O infects PE files, increasing their size by 44 KBytes.

Bagle.O spreads via e-mail in a message with variable characteristics, and an attached file with an icon similar to Windows Notepad. It can also spread through peer-to-peer (P2P) file sharing programs.

Bagle.O contains a backdoor, which opens the TCP port 2556.

In addition, Bagle.O ends the processes belonging to several antivirus programs, firewalls and system monitoring tools. It also ends the processes belonging to previous variants of the worms Bagle and Netsky.

This worm only runs if the system date is December 31, 2005 or previous. After this date, Bagle.O stops functioning.

Visible Symptoms 


Bagle.O is easy to recognize, as it reaches the computer in an e-mail message with an attached file that has an icon similar to Windows Notepad: