Why rootkits mean you must nuke your machine
Published: 17 Nov 2005 17:35 GMT
How do rootkits work?
In Windows, the easiest way for a rootkit to run is in user mode. The
easiest way for it to do this is to grab hold of the ntldll.dll file,
and if it can control this then it can hide anything it wants from any
other program running in user mode. Software may askntldll.dll if there
is a rootkit present, and if there is, it will say "No".
Other rootkits run in kernel mode, and these can fool not only user-mode scanning, but also kernel-mode scanning. That can be a big concern.
Once installed, a rootkit can do anything it wants to. It can hide files, directories, ports, registry entries, pretty much anything you might use in user mode to examine the system.
Most virus scanners cannot detect a rootkit when that rootkit is active — the scanner says "show me all the files on the operating system, and the rootkits say "ok, I'll show you all the files on the operating system (except mine)." So all the files are scanned except those belonging to, or hidden by, the rootkit.
User mode rootkits are relatively stable. If they crash then they only affect themselves. They are much more common that kernel-level rootkits. However, a lot of people try to write kernel mode rootkits, and these are inherently dangerous as they operate in a space where the operating system works. They can destabilise the entire system. They frequently bluescreen machines; in product support that is often the first sign we see that a rootkit exists on a system.
Kernel mode rootkits are more powerful but far more dangerous, as they tend to be more unstable. Why?
Because the application programmers writing them are not so advanced.
Yet. We have to see any great programmers writing kernel mode rootkits,
but this is in its infancy, so that may well change.
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5 comments
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A rootkit exists in video memory?? Is this video m... Anonymous -
wouldn't it solve the problem if the OS does not a... Sans
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This article is woefully uninformed, from the mean... Anonymous
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Rootkits should be viwed exactly the same as other... Martin Ridley
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Try reading and fixing the terribly high amount of... Myles
