This question's explanation and your answers so far.
次の事例に該当する攻撃はどれか。 〔事例〕 広報担当の A 氏宛てに, 新聞社を名乗る相手から取材依頼の電子メールが届いた。送信元がフリーメールのアドレスであり, 本文には URL とその参照を促す記載がされていた。A 氏は不審に思い, セキュリティ部門に連絡した。セキュリティ部門が調査を行った結果, この URL にアクセスするとウイルスに感染し, PC 内部の情報が全てインターネットへ送信されるおそれがあることが判明した。また, 同様のメールが各事業部の広報担当者にも届いていた。
A dictionary attack is a password-cracking method that breaks through authentication by trying dictionary words and common passwords one after another. It has nothing to do with this case, which steals information by impersonating the sender in an email.
Spam email refers to nuisance email (such as advertisements) sent indiscriminately to a large, unspecified number of recipients. This case pinpoints a specific role (public-relations representative) rather than sending indiscriminately, so it does not fit.
正解 An attack that targets a specific organization or individual (here, the role of public-relations representative in each business division), disguises itself as content that could plausibly arise in business (an interview request from a newspaper company) to win the recipient's trust, gets them to open a URL or attachment to infect the PC with a virus, and steals information from inside the PC to the outside is called a targeted attack. The case has all the hallmarks: impersonating someone else, pinpointing a specific role, and luring the target into malware aimed at stealing information, making it a typical targeted attack, so choice is correct.
An email bomb is a harassment or disruption attack that overwhelms the target's mailbox or server by sending a huge volume of email. This case mounts information theft against a small number of chosen targets, not disruption through mass sending.