There is always the chance that one of your employees is covertly threatening your business, even the employees you least suspect. Every business owner needs to thread the needle between monitoring employees for insider threats and maintaining a healthy work environment without overbearing surveillance.
One effective security control to mitigate insider threats is the mandatory vacation. All employees are afforded certain vacation days as part of their employment agreement. Some employees are very liberal with their vacation days, while others conserve as many as possible. It should be company policy to require employees to take at least one full week of vacation per year.
The goal of a mandatory vacation is to determine whether company resources change when a specific employee is absent. Any major changes could indicate that the vacationing employee is hatching an internal scheme. For example, say you have a handful of cashiers running the front of house. If one cashier takes a week off and suddenly, profits are up by a large percentage despite no change in business, this may indicate that some sort of embezzlement is occurring. Or perhaps your firewall and intrusion detection system have been detecting a large volume of outbound traffic all year, and suddenly, the volume of traffic decreases when an employee takes a vacation, but then returns to normal volume when they return to work. This may indicate that said employee is exfiltrating company data to a third party.
It is important not to rely on trends detected during a mandatory vacation alone as an indicator of guilt. You will end up with a toxic workplace if you latch on to any little thing that changes when a certain employee is gone and wave that around as an indicator of malicious activity. The goal is to closely study trends and combine them with other evidence to gather insights into potential insider threats. Mandatory vacations alone also will not mitigate insider threats. However, they can be an effective part of workplace security that should be considered.