What is a common use of botnets?

Botnets are commonly used to execute Distributed Denial of Service (DDoS) attacks. A botnet is a collection of compromised computers or devices that are controlled remotely by an attacker. These devices, often referred to as "bots" or "zombies," can be coordinated to send a large volume of traffic to a specific target, overwhelming its resources and causing disruption or outages.

In a DDoS attack, the intent is to exhaust the target's bandwidth, processing capacity, or application resources. By utilizing a network of bots, attackers can generate an attack traffic level far beyond what an individual computer could achieve, making DDoS attacks particularly damaging and difficult to mitigate.

Other options like data encryption, email security, and VPN services do not represent typical uses of botnets. Data encryption is a method of securing information, email security aims to protect email communications, and VPN services establish secure connections over the internet. None of these uses relate to the malicious intent or capabilities associated with botnets.