DETECTING UNAUTHORIZED DEVICES AT TRANSACTION DEVICES

Method and Device (100) for detecting an unauthorized device in a card slot of a transaction device, comprising: a card slot insert (110) having a width and thickness based on a manufactured width and thickness of the card slot of the transaction device; a first indicator indicating that the card slot is secure; and a second indicator indicating that the card slot is not secure. The indicators are provided at the card slot insert, such that. when the card slot insert (110) is inserted to a manufactured depth of the card slot, the first indicator is visible outside the card slot, and the second indicator is not visible outside the card slot; and, when the unauthorized device is in the card slot, the first indicator and at least a portion of the second indicator are visible outside the card slot. This is to increase security during interaction of a user's transaction card with a transaction device in view of potentially attached one or more skimmers.