Which of the following is a common type of malware?

Ransomware is a prevalent type of malware designed to extort money from users or organizations by restricting access to their data or device functions until a ransom is paid. It typically encrypts files on the victim's system and demands payment in cryptocurrency to provide the decryption key. This form of malware has become increasingly common due to its effectiveness in exploiting vulnerabilities in systems, the rise of online payment methods, and the fear it instills in victims, which can lead them to comply with demands.

In contrast, applications like calculators and spreadsheets are legitimate software used for daily computations and managing data, not malware. P2P (peer-to-peer) software is a method of sharing files and data across networks, which may be used for both legitimate and illegitimate purposes, but it is not inherently malicious. Therefore, ransomware stands out as a clear example of malware due to its malicious intent and impact on users.