1. A Linux daemon that executes specified tasks at a designated time or interval (can be daily, weekly, etc....). From I-gloss

2. On UNIX, the cron daemon automated background tasks (such as backups or rotating the logs). It is really the simplest of programs; it reads instructions from a file and executes the appropriate programs at the scheduled time. Key point: When the machine is compromised, intruders will often put backdoor jobs into the crontab. When the victim tries to clean up his/her machine, the jobs in the crontab will run giving the intruder control again. This sort of thing happened in the famous attack against the New York Times; they kept cleaning up the machine, but cron kept giving control back to the intruder. Typically, these jobs would run during the wee hours of the morning when nobody is looking. From Hacking-Lexicon

3. management of regular background processing cron is a background process (`daemon') that runs programs at regular intervals (for example, every minute, day, week or month); which processes are run and at what times are specified in the `crontab'. Users may also install crontabs so that processes are run on their behalf, though this feature can be disabled or restricted to particular users. Output from the commands is usually mailed to the system administrator (or to the user in question); you should probably install a mail system as well so that you can receive these messages. This cron package is configured by default to do various standard system maintenance tasks, such as ensuring that logfiles do not grow endlessly and overflow the disk. The lockfile-progs package is only a "Suggests" because of the poor way that dselect handles "Recomments", but I do strongly suggest that you install it; it prevents /etc/cron.daily/standard from running multiple times if something gets jammed. From Debian 3.0r0 APT