IPA IP 2020 Question 93
A question IPA Japan published in 令和2年度 10月 ITパスポート試験 公開問題 問93, translated into English. ITPEC is based on the same exams.
In a wireless LAN, which of the following is an appropriate countermeasure against eavesdropping by interception of radio waves between a PC and an access point?
Explanation
Selecting WPA2 — radio waves can be picked up by anyone nearby, so the only defence against eavesdropping is to encrypt what is sent.
An eavesdropper does not need to connect to the access point: a receiver within range captures the frames passing between the PC and the access point. WPA2 encrypts the data in those frames (with AES), so what is captured cannot be read without the key. The other three measures only control or hinder connecting to the access point, and the traffic of legitimate users still travels in the clear.
Answer (d)
Why not others:
- •(a) — MAC address filtering refuses connections from unregistered devices, but a listener never connects; MAC addresses are also sent unencrypted and can be spoofed
- •(b) — stopping the ESSID broadcast (stealth mode) hides the network's name from casual users, but the frames are still transmitted and readable
- •(c) — a hard-to-guess ESSID makes the network harder to join by guesswork; the ESSID is not a key and encrypts nothing
Key rule: Against interception of wireless traffic, encrypt it (WPA2 or later); access restrictions such as MAC filtering or ESSID stealth stop connections, not listening.
Security · AI-written, may contain errors
This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.