Disinfection Utility
F-Secure provides the special disinfection utility to eliminate Bagle worm infections. You can download this utility from our ftp site:

Disinfection Instructions
Disinfection instructions can be found here:

System Administrators
System administrators who are using F-Secure Policy Manager, can distribute the tool as a JAR package automatically to all workstations.
The JAR version can be downloaded from:

Email-Worm:W32/Bagle.AT spreads via e-mail file attachments and through Peer-to-Peer (P2P) networks, as well as through a prepended Windows Control Panel Applet (CPL) stub.
This worm is programmed to cease its activity on Apr 25th, 2006.

Infection

Bagle.AT arrives a file attachment to an e-mail message, which has varying subject lines and body texts.  The attachment is an executable file with one the following extensions: .EXE, .SCR, .COM and .CPL. The worm uses several different icons for the attachments it sends, such as these:

When the worm's file is run, it copies itself as wingo.exe to Windows System folder and creates a startup key for this file in the Registry:

%SystemDir% represents the Windows System folder name, for example C:\Windows\System32 on Windows XP systems.

If system date is Apr 25th, 2006 the worm uninstalls itself from the infected system by deleting its startup key in the Registry and terminating its own process.
The worm creates 2 more files in Windows System folder:

These files are used when the worm spreads itself in e-mails.

Propagation (E-mail)

To find new victims, Bagle.AT scans the hard drive to collect e-mail addresses. Files with the following extensions are checked:

The worm ignores e-mail addresses that contain any of the following strings:

Bagle.AT spreads itself in e-mails with randomly-chosen subject lines, mail bodies and attachment names.  Bagle.AT uses the following text strings as subjects for infected e-mails that it sends:

Message bodies are randomly chosen from a predefined list:

Attachment names can be one of the following names with EXE, SCR, COM, and CPL extension:

When the worm copies itself in shared folder or sends itself as an e-mail attachment, it changes the icon file of the executable. The icon is picked randomly from the infected computer's hard drive.

Propagation (CPL)
When spreading as a Windows Control Panel Applet file, the worm prepends a small binary dropper to its executable file. When the CPL file is activated, it copies itself as cjector.exe file to Windows folder and then drops the worm's file into Windows System folder.

Propagation (P2P)

Bagle.AT is capable of spreading to shared folders of Peer-to-Peer clients. It scans all available drives and if it finds a folder name that contains 'shar' substring, the worm copies itself there with the following names:


Activity

The worm has a backdoor that listens on port 81. The backdoor code is encrypted with a password. The worm author who knows the password can connect to the computer and execute arbitrary programs. Infected computers are reported to the worm's author by accessing several predefined URLs.
The worm also tries to download and execute a file from list of predefined URLs. The downloaded file is saved on disk under the following name:

At the time of this writing, some of the URLs are functional. The file is a downloader that tries to access another list of predefined URLs.

Finally, Bagle.AT terminates processes of security and antivirus software as well as some other applications. Processes of the following applications are terminated:


Uninstalling the NetSky Worm

To disable the NetSky worm, Bagle.AT removes a number of registry values from under


Additionally the worm creates several MUTEXes with names that are used by NetSky worm, so that certain versions of NetSky will not infect a system where the Bagle.AT worm is active.