http://www.darkreading.com/security/vulnerabilities/showArticle.jhtml?articleID=216500687 

By Kelly Jackson Higgins
DarkReading
April 14, 2009

Kernel rootkits are tough enough to detect, but now a researcher has 
demonstrated an even sneakier method of hacking Linux.

The attack attack exploits an oft-forgotten function in Linux versions 
2.4 and above in order to quietly insert a rootkit into the operating 
system kernel as a way to hide malware processes, hijack system calls, 
and open remote backdoors into the machine, for instance. At Black Hat 
Europe this week in Amsterdam, Anthony Lineberry, senior software 
engineer for Flexilis, will demonstrate how to hack the Linux kernel by 
exploiting the driver interface to physically addressable memory in 
Linux, called /dev/mem.

"One of bonuses of this [approach] is that most kernel module rootkits 
make a lot noise when they are inserting [the code]. This one is 
directly manipulating" the memory, so it's less noticeable, he says.

The /dev/mem "device" can be opened like a file, and you can read and 
write to it like a text file, Lineberry says. It's normally used for 
debugging the kernel, for instance.

[...]


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