Linux Cron Persistence - Malicious Cron Entry

Georg Lauenstein@gsec

•updated 5 days ago•0•0•1

Detects a process launch whose command line both references a cron persistence path (crontab, /etc/cron.d/, /etc/crontab, /etc/cron.{hourly,daily,weekly,monthly}/, /var/spool/cron/crontabs/) and contains a download-and-execute or reverse-shell marker (curl/wget piped to a shell, /dev/tcp/ redirection, base64-decoded payload, nc -e) or installs the crontab from a file staged under /tmp/. Attackers commonly install a scheduled cron entry so a malicious command re-executes on a fixed interval, surviving reboots and process kills (T1053.003).