I keep getting weir cron jobs showing up and I have no clue what they do. I typically issue kill -9 to stop them. They take up 100% of my CPU and can run for days until I check. Does anyone know what this means?

sudo crontab -l

0 0 */3 * * /root/.firefoxcatche/a/upd>/dev/null 2>&1

@reboot /root/.firefoxcatche/a/upd>/dev/null 2>&1

5 8 * * 0 /root/.firefoxcatche/b/sync>/dev/null 2>&1

@reboot /root/.firefoxcatche/b/sync>/dev/null 2>&1

#5 1 * * * /tmp/.X13-unix/.rsync/c/aptitude>/dev/null 2>&1

I am running Ubuntu 18 LTS server fully up-to-date as of yesterday 7/24/2019

UPDATE

I appreciate all the feedback. I have disconnected all data and application drives since the only thing that was affected was the OS drive, I at least did that sort of thing properly. I am going with a complete rebuild, with a lot more security and more secure methods.