A Blickschutzfolie (privacy filter) is a screen protector that makes displayed content visible only from a narrow viewing angle. From the side, the screen appears dark or distorted.
In an ISMS, privacy filters address ISO 27001 Annex A controls A.7.8 (Equipment Siting and Protection) and A.6.7 (Remote Working). They are especially relevant for mobile workplaces — trains, planes, co-working spaces — where third parties could view confidential information (shoulder surfing). The filter is a simple, low-cost physical measure often included in the clean desk/clear screen policy. For laptops with high brightness, choose a filter that minimizes brightness reduction.