The rule 'Suspicious cron detected' identifies the addition of potentially malicious cron jobs through the osquery differential log type. It targets a high-severity threat level, focusing on the use of cron jobs for executing commands that may indicate nefarious activities. The detection mechanism leverages attributes such as 'action', 'hostIdentifier', and 'name' to identify suspicious entries that have been added to the crontab on a monitored system. Specific scenarios include commands that set up reverse shells using netcat, unexpected wget executions to download and execute scripts, and unintended dig commands accessing external resources. It also employs a set of predefined tests to evaluate the expected results of typical benign and malicious cron job entries. If any suspicious actions are detected in the logs, immediate analysis and validation of the command are necessary to assess the potential risk associated with the added cron job.