Which of the following is NOT a common type of cyber attack on banking systems?

Insider attacks are not as common as the other types of cyber attacks listed above. However, they can be very costly and disruptive for banking systems. Insider attacks can be carried out by employees who have authorized access to the bank's systems and data.

The other four types of cyber attacks are all common types of attacks on banking systems. Phishing attacks attempt to trick victims into revealing sensitive information, such as their passwords or credit card numbers. Ransomware attacks encrypt a victim's files and then demand a ransom payment in exchange for the decryption key. Supply chain attacks involve targeting a third-party supplier in order to gain access to the target company's systems and data. DDoS attacks attempt to overwhelm a target system with traffic, making it unavailable to legitimate users.