Which of the following best describes ransomware?

Ransomware is a specific type of malicious software that gains access to a computer or network and encrypts files, making them inaccessible to the user. The attacker then demands a ransom, typically paid in cryptocurrency, to provide the decryption key needed to restore access to the files. This type of threat is particularly damaging because it can result in significant data loss and financial cost if victims choose to pay the ransom or are unable to recover their data through other means.

The other options provided describe different types of software functionalities that are not related to ransomware. For instance, software that cleans up junk files generally refers to optimization tools that help improve system performance by removing unnecessary files, and programs that update security features focus on enhancing the protection of the system against various threats. Similarly, software that enhances browsing speed aims to improve the user’s online experience without any involvement in data encryption or ransom demands. Thus, the defining characteristic of ransomware lies in its malicious intent to extort money through data encryption.