Bagle.U (Beagle.U in Symantecs dictionary) is a very simple worm. The e-mail message in which it arrives has no subject line or body. The attachment has a randomized file name with an .EXE extension. The user must launch the executable.
Many e-mail clients, including all recent versions of Microsoft Corp.s Outlook and Outlook Express strip all .EXE attachments, so those users will be protected against Bagle.U.
The Norman analysis of the worm states that when a user does receive and launch the executable, it places a copy of itself, named GIGABIT.EXE, in the %SysDir% directory (%SysDir% is a system variable usually equivalent to C:\WINDOWS\SYSTEM or something similar). It also sets a registry key to launch that program when the system starts.
According to McAfees description of the worm, it also creates the HKEY_CURRENT_USER\Software\Windows2004 key and places two values, "fr1n" and "gsed," within it.
Panda Software states that the worm also creates a backdoor on TCP port 4751, meaning that it listens on that port for external commands. It also attempts to connect to the script at http://www.werde.de/5.php, presumably to notify someone of the infection. Finally, it launches the program MSHEARTS.EXE, a card game that comes standard with Windows.
Bagle.U will stop running after Jan. 1, 2005.
Even though it contains none of the innovations in other recent worms, all of the major anti-virus companies have classified this worm as an elevated threat, and Panda has classified it as a "High" threat due to the extent of spreading.
Ken Dunham, director of Malicious Code for iDefense Inc., believes that the initial successful spread of the worm comes from a more widespread seeding of the worm. This refers to the initial choice of worm recipients by the worms author.
Editors Note: This story was updated to include information from Ken Dunham.
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