You can't get close enough to the facility interior to launch an evil twin attack against its wireless clients; in fact, you haven't even discovered their SSIDs. What you have discovered is a number of employees eating lunch in a park outside on warm afternoons. What kind of evil twin attack can target those users' laptops and smartphones

In evil twin attack, the hacker can steal these users, user names and passwords to use them in fraudulent activities.

Explanation:

In Evil twin attack, hacker creates an access point with the same SSID as the nearest WiFi provider have. He block the SSID of internet provider for the end users and end users will access through SSID provided by the hacker. That is the reason this is called Evil Twin Attack.

In evil twin attack, the hacker can steal the password and user ID of the users to use them in fraudulent activities, can access their passwords and bank account numbers.

In above given case, where hacker does not know the SSID of any user, he may steal the User ID and passwords of all users using evil twin attack to involve them in fraudulent activities.