Rootkits

Rootkits are "malicious software", just like viruses and worms. Rootkits are special because they are almost impossible to detect.

The name "Rootkit" was derived from the superuser name in UNIX, called "root". This root user has all rights on a system, just like the Windows Administrator has. By the way, rootkits are a problem of all operating systems, including Windows.

Rootkits and other malicious software can create backdoors in systems. Using this backdoor, hackers can penetrate the system to use it, to damage it (erasing or destroying data) or to use the system for attacks on other systems.

Rootkits are very hard to detect because they not only install malicious software, but they also install software that replace system commands. An example is the UNIX/Linux commando 'ls -l'. This command is used to print a list of files on the screen:

$ ls -l
total 72
drwxr-xr-x 3 slaan slaan 4096 2006-09-14 11:02 BACKUP
drwxr-xr-x 9 slaan slaan 4096 2006-09-16 13:52 google-earth
-rwxrwxrwx 1 slaan slaan 150 2006-10-02 19:50 maliciouscode.exe
drwxr-xr-x 8 slaan slaan 4096 2006-05-05 09:44 Murdoc_development
drwxrwxrwt 7 slaan slaan 4096 2006-09-10 13:54 My Virtual Machines
drwxr-xr-x 2 slaan slaan 4096 2006-09-15 08:45 scripts
drwxr-xr-x 11 slaan slaan 4096 2006-09-25 15:35 uapplications
drwxr-xr-x 2 slaan slaan 4096 2006-09-12 21:42 vmware

A rootkit could install a new version of 'ls'. This way the malicious code becomes invisible:

$ ls -l
total 72
drwxr-xr-x 3 slaan slaan 4096 2006-09-14 11:02 BACKUP
drwxr-xr-x 9 slaan slaan 4096 2006-09-16 13:52 google-earth
drwxr-xr-x 8 slaan slaan 4096 2006-05-05 09:44 Murdoc_development
drwxrwxrwt 7 slaan slaan 4096 2006-09-10 13:54 My Virtual Machines
drwxr-xr-x 2 slaan slaan 4096 2006-09-15 08:45 scripts
drwxr-xr-x 11 slaan slaan 4096 2006-09-25 15:35 uapplications
drwxr-xr-x 2 slaan slaan 4096 2006-09-12 21:42 vmware

To prevent this to be noticed, incorrect information about the 'ls' command itself is showed by the patched 'ls' command. This hides files with incorrect sizes. If necessary, rootkits could even change the kernel to make it show incorrect values!

There are two ways to prevent rootkits from being installed: 

  1. Using virus detection, the installation of rootkits can be avoided;
  2. Using Host-based-IDS (Intruder Detection Systems) technology changes to the system can be detected.

Both methods are very delicate however: Circumventing virus scanners can be done already and IDS systems can be misguided by rootkits, just like it misguides other applications and commands.

In 2005 rootkits made the news when it was uncovered that record company Sony/BMG installed rootkits, using their music CD's, to secretly install copy protection software. Eventually, it cost Sony much more than it gained. Client's trust was damaged which cost a lot more than a few illegally copied CD's.


This entry was posted on Friday 08 December 2006

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IT Infrastructure model

Sjaak Laan


Recommended links

Ruth Malan
Gaudi site
Byelex
XR Magazine
Esther Barthel's site on virtualization


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The postings on this site are my opinions and do not necessarily represent CGI’s strategies, views or opinions.

 

Copyright Sjaak Laan