Bifrost (trojan horse)

Computer virus
Fullname = Bifrost trojan horse family
Common name = Bifrost
Technical name = Bifrost
Family = Bifrose
Aliases = (Windows Metafile vulnerability-related: Backdoor-CEP, Bifrost), Backdoor-CKA, Agent.MJ
Classification = Trojan
Type = Windows 95, Windows 98, Windows Me, Windows NT, Windows 2000, Windows XP, Windows Server 2003
Subtype = Backdoor
IsolationDate = 2004 - present
Isolation = Unknown
Origin = Sweden
Author = ksv

Bifrost is a backdoor trojan horse family of more than 10 variants which can infect Windows 95 through Vista. Bifrost uses the typical server, server builder, and client backdoor program configuration to allow a remote attacker, who uses client, to execute arbitrary code on the compromised machine (which runs the server whose behavior can be controlled by the server editor).

The server component (29,053 bytes) is dropped to C:Program FilesBifrostserver.exe with default settings and, when running, connects to a predefined IP address on TCP port 81, awaiting commands from the remote user who uses the client component. It can be assumed that once all three components are operational, the remote user can execute arbitrary code at will on the compromised machine.

The server builder component has the following capabilities:
* Create the server component
* Change the server component's port number and/or IP address
* Change the server component's executable name
* Change the name of the Windows registry startup entry
* Include rootkit to hide server process
* Include extensions to add features (adds 22,759 bytes to server)
* Use persistence (makes the server harder to remove from the infected system)

The client component has the following capabilities:
* Process Manager (Browse or kill running processes)
* File manager (Browse, upload, download, or delete files)
* Window Manager (Browse, close, maximize/minimize, or rename windows)
* Get system information
* Extract passwords from machine
* Keystroke logging
* Screen capture
* Webcam capture
* Desktop logoff, reboot or shutdown
* Registry editor
* Remote shell

On December 28, 2005, the Windows WMF exploit was used to drop new variants of Bifrost to machines. Some workarounds and unofficial patches were published before Microsoft [http://www.microsoft.com/presspass/press/2006/jan06/01-05UpdatePR.mspx announced] and issued an official patch on January 5, 2006. The WMF exploit is to be considered extremely dangerous.

Older variants of Bifrose used different ports, e.g. 1971, 1999; had a different payload, e.g. C:Winntsystem32system.exe; and/or wrote different Windows registry keys.

See also

*Windows Metafile vulnerability

External links

* [http://vil.nai.com/vil/content/v_125294.htm BackDoor-CEP] , by McAfee, covers server behavior of a Bifrose variant dropped exploit WMF
* [http://vil.nai.com/vil/content/v_125295.htm BackDoor-CEP.cfg] , by McAfee, covers client and server editor behavior of said Bifrose variant
* [http://vil.mcafeesecurity.com/vil/content/v_128889.htm Backdoor-CKA] , by McAfee
* [http://securityresponse.symantec.com/avcenter/venc/data/backdoor.bifrose.html Backdoor.Bifrose] , by Symantec
* [http://www.sarc.com/avcenter/venc/data/backdoor.bifrose.c.html Backdoor.Bifrose.C] , by Symantec
* [http://www.sophos.com/virusinfo/analyses/trojbifroseaj.html Troj/Bifrose-AJ] , by Sophos
* [http://www.chasenet.org ChaseNET] , Bifrost Homepage
* [http://www.megasecurity.org/trojans/b/bifrost/Bifrost1.2.1.html Bifrost 1.2.1] , by MegaSecurity