問52
頻出度★★★
DoS (Denial of Service) 攻撃の説明として, 適切なものはどれか。
平成25年度 春期 ITパスポート試験 問52
テクノロジ系セキュリティ › 情報セキュリティ
This question's explanation and your answers so far.
解説
問 52
Incorrectア
“Impersonating another person to illegitimately use services on a network” describes unauthorized access carried out through impersonation (spoofing). Using a stolen user ID and password, the attacker poses as the legitimate person and uses services for which he or she has no authorization; the core of it is a violation of confidentiality. Both its purpose and its method differ from a DoS attack, which shuts down the service itself.
Incorrectイ
“Peeking at another person's data along a communication path” describes eavesdropping (sniffing). It is a passive attack that secretly intercepts the packets flowing over the network and reads their contents, and what it violates is confidentiality. It does not amount to a DoS attack, which sends huge numbers of requests to take availability away.
- ウ
正解 The correct answer is ウ. A DoS (Denial of Service) attack is, exactly as its name says, an attack that brings about a “denial of service”: it sends the target server or network more data or more requests than it can process, uses up resources such as line bandwidth, CPU, and memory, and drives the system into a state where legitimate users cannot use the service. Concretely, it takes forms such as flooding a mail server with huge volumes of email, or sending huge numbers of web requests so that the web server stops responding. Its aim is not to steal information but to stop the service; in other words, its greatest characteristic is that it directly violates availability, one of the three elements of information security. Choice ウ, “Sending large volumes of email, web requests, and the like to make services on a network unavailable,” is exactly this definition, so it is appropriate. Note that the distributed form, in which a DoS attack is launched all at once from many stepping-stone computers, is called a DDoS (Distributed DoS) attack.
Incorrectエ
“Trying to crack a password by sequentially testing combinations of characters” describes a brute-force attack (exhaustive search). It is a technique that tries every conceivable password one after another in an attempt to break through authentication; its aim is unauthorized login, not stopping a service.
ここがポイント
- DoS (Denial of Service) attack = an attack that sends large volumes of email, requests, and the like to exhaust resources so that legitimate users cannot use the service. What it violates is availability, one of the three elements of information security. The distributed form, launched all at once from many stepping-stone computers, is a DDoS attack.
- Distinguish similar attack terms by what they violate: impersonation (posing as someone else to use a service illegitimately) and eavesdropping (intercepting the content of communications) mainly harm confidentiality, while a brute-force attack (cracking a password by exhaustively trying combinations) aims at breaking through authentication. None of them is the same thing as a DoS attack.
用語