chkrootkit

The chkrootkit security scanner searches for signs that the system is infected with a ‘rootkit’. Rootkits are a form of malware that seek to exploit security flaws to grant unauthorised access to a computer or its services, generally for malicious purposes.

chkrootkit can identify signs of over 70 different rootkits (see the project’s website for a list).

Please note that an automated tool like chkrootkit can never guarantee a system is uncompromised. Nor does every report always signify a genuine problem: human judgement and further investigation will always be needed to assure the security of your system.

Installed size: 966 KB
How to install: sudo apt install chkrootkit

chklastlog

Check lastlog file for deleted entries

root@kali:~# man chklastlog
CHKLASTLOG(8)               System Manager's Manual               CHKLASTLOG(8)

NAME
       chklastlog - check lastlog file for deleted entries

SYNOPSIS
       chklastlog  looks for users whose login has been erased from the lastlog
       database.

DESCRIPTION
       chklastlog reads all entries from /var/log/wtmp (a database of  informa-
       tion  about logins and logouts) and checks that every user found in this
       file has an entry in /var/log/lastlog.  It lists any users  with  logins
       in  wtmp but no lastlogin information. This may suggest the user account
       has been compromised and the attacker has tried to cover their tracks.

       chklastlog needs to be able to read /var/log/wtmp  and  /var/log/lastlo-
       gin.   Normally  these files are world-readable so no special privileges
       are required.

FILES
       /var/log/wtmp
              database of logins and logouts.

       /var/log/lastlog
              database which contains info on the last login of each user.

SEE ALSO
       wtmp(5), who(1), lastlog(8), last(1)

LIMITATIONS
       wtmp may itself be incomplete because not all  programmes  record  their
       activity using utmp logging. See wtmp(8).

       chklastlog will not detect missing entries if the user has logged in af-
       ter the lastlog entry was deleted.

       This  program  was  originally  designed to run on SunOS 4.x systems. On
       other systems the output is undefined.

                                  Oct 23, 2021                    CHKLASTLOG(8)

chkrootkit

Scan the system for signs of rootkits

root@kali:~# chkrootkit -h
Usage: /usr/sbin/chkrootkit [options] [test ...]
Options:
        -h                show this help and exit
        -V                show version information and exit
        -l                show available tests and exit
        -d                debug
        -q                quiet mode
        -x                expert mode
        -e 'FILE1 FILE2'  exclude files/dirs from results. Must be followed by a space-separated list of files/dirs.
                          Read /usr/share/doc/chkrootkit/README.FALSE-POSITIVES first.
        -s REGEXP         filter results of sniffer test through 'grep -Ev REGEXP' to exclude expected
                          PACKET_SNIFFERs. Read /usr/share/doc/chkrootkit/README.FALSE-POSITIVES first.
        -r DIR            use DIR as the root directory
        -p DIR1:DIR2:DIRN path for the external commands used by chkrootkit
        -n                skip NFS mount points
        -T FSTYPE         skip mount points of the specified file system type

chkrootkit-daily

Run chkrootkit and report results

root@kali:~# man chkrootkit-daily
chkrootkit-daily(8)         System Manager's Manual         chkrootkit-daily(8)

NAME
       chkrootkit-daily - Run chkrootkit and report results

SYNOPSIS
       chkrootkit-daily

DESCRIPTION
       chkrootkit-daily  runs  chkrootkit(8)  and emails the results. It is in-
       tended to be run by the systemd(1) timer or as a cron(1) job every day.

CONFIGURATION
       All options are set and documented in /etc/chkrootkit/chkrootkit.conf.

AUTHOR
       chkrootkit-daily and this manual page were written by Richard Lewis  for
       the Debian project. They may be used by others.

SEE ALSO
       chkrootkit(8)

                                   2023-02-19               chkrootkit-daily(8)

chkwtmp

Check wtmp file deleted entries

root@kali:~# man chkwtmp
CHKWTMP(8)                  System Manager's Manual                  CHKWTMP(8)

NAME
       chkwtmp - check wtmp file deleted entries

SYNOPSIS
       chkwtmp looks for data deleted from wtmp

DESCRIPTION
       chkwtmp  examines  the  file  /var/log/wtmp  for entries which have been
       overwritten (containing only null-bytes). If such entries are found  the
       program  displays  the  timestamps  of  the entries before and after the
       deleted entry, providing an idea of when the entry was deleted.

       chkwtmp needs to be able to read /var/log/wtmp.  Normally this  file  is
       world-readable so no special privileges are required.

FILES
       /var/log/wtmp
              database of logins and logouts.

SEE ALSO
       wtmp(4), who(1)

LIMITATIONS
       An  entry  is recognized as overwritten if the time-information has been
       overwritten with null-bytes.

       This program was originally designed to run on  SunOS  4.x  systems.  On
       other systems the output is undefined.

                                  Oct 23, 2021                       CHKWTMP(8)

Learn more with OffSec

Want to learn more about chkrootkit? get access to in-depth training and hands-on labs:

• PEN-103: 8.5.3. Securing and Monitoring Kali Linux: Detecting Changes

PEN-103 course