A penetration tester is performing an assessment for an organization and must gather valid user...

 Deauthentication attacks can force legitimate users to disconnect from a wireless network, prompting them to reconnect and, in the process, capture valid user credentials using a rogue access point or network monitoring tools.

 Details:

A. Wardriving: Involves driving around to discover wireless networks; it does not directly gather user credentials.

B. Captive portal: Requires users to log in but is not an attack method; it is a legitimate method to control network access.

C. Deauthentication: Forces users to reauthenticate, allowing an attacker to capture credentials during the reconnection process.

D. Impersonation: Involves pretending to be someone else to gain access but is less effective for directly capturing user credentials compared to deauthentication.

 References: Deauthentication attacks are well-documented in wireless security assessments and penetration testing guides.