Will specifying a dedup period delay an alert for the duration of the set period?
No, the dedup period will not delay an alert for the period it is set to. Instead, it adds more triggers of the rule to the same alert over the set dedup period.
Dedup works by grouping similar alerts together. When you first get a positive rule match, an alert is generated and delivered. For future or subsequent rule matches within that dedup period, we attach those matches to the first alert and do not send another alert notification. This is to avoid spamming.
Here is an example, if we have a rule with a dedup period of 1 hour:
10:07 - first rule match -> fires alert 10:36 - second rule match -> attached to first alert 10:42 - another rule match -> attached to first alert 11:06 - another match -> attached to first alert 11:07 - another match -> fires new alert, since it's been 1 hour (or more) since we got the first event 11:12 - another match -> get's attached to the second alert ...
Please see Panther's documentation on Deduplication for more information.