Final answer:
The malware infecting Gabriel's sister's computer is called Blocking ransomware. This malware restricts access and demands a ransom, and it's important not to pay but seek professional help.
Step-by-step explanation:
The type of malware that has infected Gabriel's sister's computer is b. Blocking ransomware. This type of malware typically restricts access to the computer or files and demands a ransom to be paid to restore access. It's a form of cyber extortion where the attacker claims control of the victim's system until the demand is met. It is crucial not to pay the ransom as it does not guarantee the restoration of access and can potentially expose the victim to further attacks.
Instead, Gabriel's sister should disconnect the computer from the internet to prevent any further damage and contact a professional for assistance. This might include using antivirus and anti-malware tools, restoring the system from backups, or seeking help from law enforcement or cybersecurity experts. Her next steps should also include changing all her passwords and monitoring her accounts for any signs of unauthorized access.