問66
頻出度★★★
データを暗号化することによって防ぐことのできる脅威はどれか。
平成26年度 春期 ITパスポート試験 問66
This question's explanation and your answers so far.
解説
問 66
Incorrectア
Deletion of data caused by mistaken operation cannot be prevented by encryption. Even encrypted data is gone once the file is deleted, because encryption is not a technology for keeping data from disappearing. This is an issue of availability and integrity among the three elements of information security, and the effective countermeasures are taking backups, properly setting access rights (write and delete permissions), and providing confirmation dialogs before deletion or well-defined operating procedures.
Incorrectイ
Social engineering is a technique that steals information by exploiting gaps in human psychology and behavior rather than technical weaknesses of a system. Typical examples are impersonating a manager or a business partner to ask for a password over the phone, looking at a screen over someone's shoulder (shoulder hacking), and digging through documents in the trash (trashing); all of them still work even when the data is encrypted. The countermeasures are not technical but mainly operational and human: employee training, strict identity verification procedures, and shredding documents.
- ウ
正解 The correct answer is ウ, eavesdropping on communication contents. Encryption is a technology that uses a fixed set of rules (an algorithm) together with a key to convert data into a form (ciphertext) whose meaning cannot be read by a third party. Only a party holding the correct key can decrypt it back into the original data (plaintext). Data flowing over a network may be intercepted by a third party somewhere along the route, but if it has been encrypted in advance, the contents cannot be understood even if the data itself is stolen and looked at. In other words, what encryption protects is confidentiality (only authorized people can see the information), one of the three elements of information security, and eavesdropping is exactly a threat to confidentiality, so encryption is an effective countermeasure. Familiar examples include HTTPS communication in web browsers and WPA2 on wireless LANs, both of which use encryption to prevent eavesdropping on communication contents.
Incorrectエ
A DoS attack (denial-of-service attack) is an attack that sends a huge volume of communication or processing requests to a server to overload it, putting the service into a state where legitimate users cannot use it. What is targeted is not the contents of the data but the availability of the service, so encrypting the stored data cannot prevent the server from going down. The countermeasures need to be mechanisms that raise availability, such as blocking illegitimate traffic with a firewall or IPS, limiting traffic volume, and using load balancing or redundant configurations.
ここがポイント
- Encryption is a technology for keeping a third party without the key from reading the contents of data, and what it can protect is confidentiality among the three elements of information security. It is therefore effective against threats of the kind where the contents become known to others, such as eavesdropping and peeking, but has no effect against threats where data disappears (availability and integrity).
- Remember threats and countermeasures by pairing them according to what is being protected. Eavesdropping goes with encryption, accidental deletion with backups and access-right settings, social engineering with human and operational countermeasures such as training, and DoS attacks with availability countermeasures such as firewalls and redundancy; organizing them this way helps.
用語