Torna alla DocumentazioneEven a well-configured VPS can be compromised. These tools help detect:
- rkhunter: rootkits, backdoors, modified system files
- ClamAV: viruses, malware, suspicious files in user directories
rkhunter: Rootkit Detection
Installation
# Debian / Ubuntu
apt install rkhunter -y
# AlmaLinux / CentOS
dnf install rkhunter -y
Initial Configuration
# Update the database
rkhunter --update
# Record the current "good" state of the system
rkhunter --propupd
Run --propupd BEFORE installing new software, otherwise rkhunter will report false positives for the new files.
Manual Scan
rkhunter --check --sk
Typical clean output:
System checks summary
=====================
File properties checks...
Files checked: 148
Suspect files: 0
Rootkit checks...
Rootkits checked : 497
Possible rootkits: 0
Applications checks...
All checks skipped
The system checks took: 1 minute and 24 seconds
All results have been written to the log file: /var/log/rkhunter.log
Email Alert Configuration
nano /etc/rkhunter.conf
# Email notifications
MAIL-ON-WARNING="admin@yourdomain.com"
MAIL_CMD=mail -s "[rkhunter] Warning found on $(hostname)"
# Show only warnings (not info)
REPORT_EMAIL_WARNINGS_ONLY=1
# Whitelist common false positives
SCRIPTWHITELIST=/usr/sbin/adduser
SCRIPTWHITELIST=/usr/bin/ldd
Automation with cron
crontab -e
# Scan every day at 3:00 AM
0 3 * * * /usr/bin/rkhunter --cronjob --update --quiet 2>&1 | mail -s "rkhunter $(hostname)" admin@yourdomain.com
ClamAV: Antivirus
Useful for servers that handle file uploads (hosting, mail server, FTP).
Installation
# Debian / Ubuntu
apt install clamav clamav-daemon -y
# AlmaLinux / CentOS
dnf install clamav clamd clamav-update -y
Update Virus Database
# Stop the daemon temporarily for update
systemctl stop clamav-freshclam
freshclam
systemctl start clamav-freshclam
Scan Directories
# Scan /var/www with automatic removal of infected files
clamscan -r /var/www --remove --log=/var/log/clamav-scan.log
# Scan without removing (report only)
clamscan -r /home --log=/var/log/clamav-scan.log
# Only infected files in report
clamscan -r /var/www -i --log=/var/log/clamav-scan.log
Weekly Automation
crontab -e
# Every Sunday at 2:00 AM
0 2 * * 0 /usr/bin/clamscan -r /var/www -i --log=/var/log/clamav-weekly.log && mail -s "ClamAV scan $(hostname)" admin@yourdomain.com < /var/log/clamav-weekly.log
ClamAV Daemon (Real-Time Scanning)
For mail servers or upload file servers, enable the daemon:
systemctl enable --now clamav-daemon
systemctl status clamav-daemon
Recommended Workflow
rkhunter often reports Perl files, system scripts, and updated binaries. Always check the log before alarming. Use ALLOWHIDDENDIR and SCRIPTWHITELIST in rkhunter.conf to exclude confirmed false positives.
- At server setup: install both, run rkhunter --propupd
- Weekly: automatic rkhunter + ClamAV scan of public directories
- On anomalies: full manual scan + analyze /var/log/rkhunter.log
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