Most Damaging Malware

[Gnosis]

All malware is bad, but some types of malware do more damage than others. That damage can range from loss of files to total loss of security -- even outright identity theft. This list (in no particular order) provides an overview of the most damaging types of malware, including viruses, Trojans and more.

http://antivirus.about.com/od/virusdescriptions/tp/worstvirus.htm

 

[Nikos]

Rootkits
A rootkit gives attackers full access to the system (hence the term 'root') and typically hides the files, folders, registry edits, and other components it uses. In addition to hiding itself, a rootkit typically hides other malicious files that it may be bundled with. The Storm worm is one example of rootkit-enabled malware. (Note that not all Storm Trojans are rootkit-enabled).

Bootkits
While said to be more theory than practice, this form of hardware targeting malware is perhaps the most concerning. Bootkits infect flash BIOS, causing the malware to be loaded even prior to the OS. Combined with rootkit functionality, the hybrid bootkit can be near impossible for the casual observer to detect, much less to remove.
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Question:

i know that in order for someone to update hits Flash Bios need to to create a bootable usb key that has flash.exe in it for start the update process in an MS-DOS/Free-DOS Enviroment.

How a "BootKit" injects a Flash Bios to embed malware code in it from within Windows Enviroment?
That contradicts the Flash Bios Update process which needs to take place from a bootable media in a non-win enviroment or even from within the Bios GUI itself.