DDoS means Distributed Denial of Service and what that means is that it spams a target with so many requests to the point that the target is slow and inoperable or crashes.
DDoS works by a cracker sending the command to initiate the attack to his zombie army. Each computer within the army sends an electronic connection request to an innocent computer called a reflector. When the reflector receives the request, it looks like it originates not from the zombies but from the ultimate victim of the attack. The reflectors send information to the victim system, and eventually the system’s performance suffers or it shuts down completely as it is inundated with multiple unsolicited responses from several computers at once. From the victim’s perspective, it looks like the reflectors attacked the system. From the perspective of the reflectors, it seems like the victimized system requested the packets. The zombie computers remain hidden, and even more, out of sight is the cracker himself.

DDoS
Distributed Denial of Service Attack (DDoS) is A denial of service (DoS) attack that is a malicious attempt to make a server or a network resource unavailable to users, usually by temporarily interrupting or suspending the services of a host connected to the Internet.
In this article, the DDoS attack tried to prevent people from making an unofficial vote on who Hong Kong wanted as a preferred political representative.
Cloudflare helped prevent the attack by tipping the traffic into sinkholes (DNS sinkholes) the DNS kept sending the data to a dead end so the attack could never hit Cloudflare or popvote.hk

Phishing
Phishing is a technique used to gain personal information for identity theft, using fraudulent e-mail messages that appear to come from legitimate businesses.

Virus
A segment of self-replicating code planted illegally in a computer program, often to damage or shutdown a system or network.

Worm
A program or algorithm replicates itself over a computer network and usually performs malicious actions, such as using up the computer’s resources and possibly shutting the system down. 
In this article, the worm acts as a normal file, but when you click on it, your computer cannot read it. When the worm is installed on your computer, it can use a keystroke program, so it sees everything you type, ranging from credit card numbers to names and social security.

Trojan horse (software version)
A Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data to get control and do its chosen form of damage.

Physical Access (Accessing a computer system in person, not through a network)
Physical access refers to actual hands-on, on-site access to a computer and network hardware or other parts of a hardware installation. Key issues with physical access revolve around security and authenticated use of hardware environments, from typical workstation cubicles to server rooms and other places where unauthorized physical access could lead to security risks.
In this article, people stole two unencrypted laptops from a senate panel and the data contained more than 840,000 policy holder’s information including social security and medical information.

Password Attacks
A method used to break security systems, specifically password-based security systems, in which the attacker systematically tests all possible passwords beginning with words that have a higher possibility of being used, such as names and places. The word “dictionary” refers to the attacker exhausting all of the words in a dictionary in an attempt to discover the password. Dictionary attacks are typically made with software instead of an individual manually trying each password.
In this article, utilities such as energy, water, nuclear, and transportation were hacked because of security flaws that made it easy for a software program to try different passwords to gain control of the internet-facing utility. This was gained by using SCADA (supervisory control and data acquisition)

Spyware
Any software that covertly gathers user information through the user’s Internet connection without his or her knowledge, usually for advertising purposes. Spyware applications are typically bundled as a hidden component of freeware or shareware programs that can be downloaded from the Internet; however, it should be noted that the majority of shareware and freeware applications do not come with spyware. Once installed, the spyware monitors user activity on the Internet and transmits that information in the background to someone else. Spyware can also gather information about e-mail addresses and even passwords and credit card numbers.