Packages and Binaries:
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.
How to install:
sudo apt install chkrootkit
Check lastlog file for deleted entries
[email protected]:~# 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 after 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)
Scan the system for signs of rootkits
[email protected]:~# 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 mounted dirs
Run chkrootkit and report results
[email protected]:~# 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)
Check wtmp file deleted entries
[email protected]:~# 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)
Updated on: 2023-May-16