Linux Detecting / Checking Rootkits with Chkrootkit and rkhunter Software

by on January 21, 2008 · 6 comments· LAST UPDATED January 21, 2008

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Q. Most rootkits use the power of the kernel to hide themselves, they are only visible from within the kernel. How do I detect rootkits under CentOS or Debian Linux server?

A.. A rootkit is a program (or combination of several programs) designed to take fundamental control (in Unix terms "root" access, in Windows terms "Administrator" access) of a computer system, without authorization by the system's owners and legitimate managers.

Detecting rootkits under Linux

You can try the following tools to detect Linux rootkits:

WARNING! These examples should run from Live CD (Linux Live Security CD) for the best result.

Zeppoo Software

Zeppoo - Zeppoo allows you to detect rootkits on i386 and x86_64 architecture under Linux, by using /dev/kmem and /dev/mem. Moreover it can also detect hidden tasks, connections, corrupted symbols, system calls and so many other things. Download source code here

Chkrootkit Software

Chkrootkit - chkrootkit is a tool to locally check for signs of a rootkit. Type the following command to install chkrootkit
$ sudo apt-get install chkrootkit
Start looking for rootkits, enter:
$ sudo chkrootkit
Look for suspicious strings, enter:
$ sudo chkrootkit -x | less
You need to specify the path for the external commands used by chkrootkit such as awk, grep and others. Mount /mnt/safe using nfs in read-only mode and set /mnt/safe binaries PATH as trusted one, enter:
$ sudo chkrootkit -p /mnt/safe

rkhunter software

rkhunter - rkhunter (Rootkit Hunter) is a Unix-based tool that scans for rootkits, backdoors and possible local exploits. rkhunter is a shell script which carries out various checks on the local system to try and detect known rootkits and malware. It also performs checks to see if commands have been modified, if the system startup files have been modified, and various checks on the network interfaces, including checks for listening applications. Type the following command to install rkhunter:
$ sudo apt-get install rkhunter
The following command option tells rkhunter to perform various checks on the local system:
$ sudo rkhunter --check
The following command option causes rkhunter to check if there is a later version of any of its text data files:
$ sudo rkhunter --update
The following option tells rkhunter which directories to look in to find the various commands it requires:
$ sudo rkhunter --check --bindir /mnt/safe

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{ 6 comments… read them below or add one }

1 Nulkarp March 12, 2010 at 1:24 am

Thank you, very good job

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2 Dariusz March 17, 2010 at 11:57 am

I try to run zeppoo on Centos 5.3 to no avail

[root@elc-url-vnp-10 zeppoo-0.0.4]# ./zeppoo -z FP
Kernel : 2.6.18-164.11.1.el5
Memory : /dev/kmem
open kmem:: No such file or directory

[root@elc-url-vnp-10 zeppoo-0.0.4]# ./zeppoo -r -d /dev/mem -m /dev/m -z FP
Kernel : 2.6.18-164.11.1.el5
Memory : /dev/mem
mmap : Operation not permitted

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3 Andrew Tappert October 4, 2012 at 11:50 pm

A more sophisticated and effective solution for Linux rootkit detection is Second Look. It is a Linux memory forensics product that uses kernel and process integrity verification to detect stealthy kernel- and user-mode malware. It supports all distros running 2.6- and 3-series kernels on 32- or 64-bit x86 systems. A large, continuously updated repository of reference kernels and hashes of vendor-distributed software support the fully automatic verification process. Learn more about it at http://secondlookforensics.com/.

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4 Andrew Tappert October 4, 2012 at 11:51 pm

A more sophisticated and effective solution for Linux rootkit detection is Second Look. It is a Linux memory forensics product that uses kernel and process integrity verification to detect stealthy kernel- and user-mode malware. It supports all distros running 2.6- and 3-series kernels on 32- or 64-bit x86 systems. A large, continuously updated repository of reference kernels and hashes of vendor-distributed software support the fully automatic verification process. (Full disclosure: I am one of the developers of Second Look.)

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5 qwertyuiop January 13, 2014 at 1:17 pm

what is the reason to install the tool (sudo apt-get… ) on a system you already suspect infected ? Would be interesting to have instructions how to update/run it from a DVD or other nonwritable media

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6 Elmar Stellnberger April 3, 2014 at 12:13 am

Unfortunately rkhunter and chkrootkit can not spot many rootkits as they are simply not in their database. However there are other ways in order to spot rootkits like f.i. online checksum verification as done by debcheckroot (http://www.elstel.org/debcheckroot/) which can even spot previously unknown rootkits.

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