令和2年度 ITパスポート試験問93

This question's explanation and your answers so far.

問93

頻出度★★★

無線LANにおいて, PCとアクセスポイント間の電波傍受による盗聴の対策として, 適切なものはどれか。

出典　令和2年度 ITパスポート試験問93

解説

問 93

Incorrectア
MAC address filtering is a countermeasure against unauthorized (spoofed) connections that rejects connections from any device other than registered ones; it does not encrypt the communication. If the radio waves are intercepted, the content can be read as is, so it is not a countermeasure against eavesdropping.
Incorrectイ
Stopping the ESSID (network name) broadcast (making it stealth) only makes the access point harder to notice and raises the barrier to connecting; the flowing radio waves themselves are not encrypted. Intercepted communication can still be decoded, so it is not a countermeasure against eavesdropping.
Incorrectウ
Setting the ESSID to a hard-to-guess value is likewise only a measure to hide the network name and make it hard to guess; it has nothing to do with encrypting the communication content. If the radio waves are intercepted, the content can be read, so it cannot prevent eavesdropping.
エ
正解 Eavesdropping (interception of radio waves) cannot be physically prevented in a wireless LAN, because the radio waves themselves travel through the air; therefore the countermeasure is to make the content unreadable even if it is intercepted, that is, to encrypt the communication. Option エ, WPA2, is a security standard that encrypts communication over the wireless section, so a third party without the key cannot decode the content even if they intercept the radio waves. Therefore the appropriate countermeasure against eavesdropping is エ.

ここがポイント

The essence of a countermeasure against eavesdropping (radio-wave interception) is encrypting the communication, and in a wireless LAN, choosing an encryption scheme such as WPA2 is the direct countermeasure.
Distinguish that MAC address filtering and hiding the ESSID (stopping the broadcast, using a hard-to-guess name) are countermeasures against unauthorized connections and cannot protect the content of intercepted radio waves.

用語

解答問93エ