Which type of attack plants malware on commonly accessed services?

A watering-hole attack compromises a legitimate website or service that the intended victims already trust and commonly visit. The attacker plants malicious active content, such as injected JavaScript or exploit code, so users are infected during normal browsing instead of being lured to an obviously suspicious site. The answer is Option D (Watering hole attack) because it specifically describes malware hosted on a commonly accessed service, which is the defining trait of this attack type.

Why the other options are incorrect:

A. Remote access trojans: A remote access trojan gives an attacker interactive control over a compromised host after infection.

B. Phishing: Phishing starts with social engineering: fake messages, links, or login pages. The question describes a legitimate common website being seeded with malicious JavaScript.

C. Exploit kits: Exploit kits automate exploitation after a victim reaches malicious content. They can be used inside an attack chain, but the scenario is naming the watering-hole delivery pattern.