Detailed
A rootkit (Option A) is a type of malware designed to gain administrative (root) access to a system while hiding its presence. Rootkits can manipulate system processes and files to remain undetected, making them particularly dangerous.
Trojan (Option B) is malware disguised as legitimate software but doesn't necessarily provide administrative access.
Worm (Option C) spreads across networks but doesn't grant administrative access.
Ransomware (Option D) encrypts data and demands a ransom but doesn't typically provide ongoing administrative access.
CompTIA A+ Core 2 Reference:
2.3 - Explain malware types, including rootkits and their purpose .