National leaders are updated weekly. Conference and school leaders are updated yearly.
This site has the most comprehensive list of all-time college football individual statistical leaders online. Every stat on this site is based on the NCAA official rules, not the school or conference rules (no bowl games prior to 2002). Defensive stats, not including interceptions, did not become official until 2000. That is why you will see two lists; one is the official one since 2000, the other is more inclusive with the start date based on when most schools began reporting defensive stats.
Some defensive stats are marked with a single asterisk (*). This means that bowl games were included in the statistics reported by the school, therefore, the player's per game average has been subtracted for each bowl game played.
Other defensive stats are marked with two asterisks (**). This means the value is only approximated, based on the statistics that could be found.