Few of the most popular Malware types are discussed in this section.
Malwares are usually categorized based on the method of infection.
How they spread and by their intentions, good understanding of malware types will help in building defence
against them.
The first one is Virus.
This type of malware attach themselves to clean files and do the harm.
Typical intentions of a virus include deleting or corrupting the core system files.
Trojans, these malwares appear as legitimate, often useful programs, but have malicious intent.
The name trojan is derived from the Greek mythology.
The Trojan Horse is a story from the Trojan War about how Greeks entered the independent city of Troy
and won the war.
The Greeks constructed a huge wooden horse and hit a select few force of men inside the horse.
The Greeks pretended to sail away and the Trojans, the opponents pulled the horse into the city as
a victory trophy.
That night, the Greek force crept out of the horse and opened the gates for the rest of the Greek army,
which had sailed back under cover of the night.
The Greeks entered and destroyed the city of Troy, thereby ending the war.
Similarly, Trojans enter a computer as unsuspecting software and create back doors are unauthorized
access to an attacker.
Worms this type of malware is known to spread itself using various methods, they make use of attached
storage like USB stick mapped networks share in a computer and some worms can even send their own
copies to all the email addresses in the address book.
Ransomware, ransomware are the type of malware that encrypts the files on a system and demand a ransom
in order to decrypt it.
These are very popular as they give a direct financial benefit to an attacker.
Spyware, Spywares are malwares designed to collect sensitive information like passwords, credit card numbers,
surfing habits, etc. Some spyware even take pictures and record audio using the built-in camera and
microphones.
Adwares, adwares or not usually malicious in nature, but are designed to serve you adds.
However, adwares can be a gateway to other malwares on your system.
Also, these adwares consume system resources rendering the computer slow.
Botnet.
The word botnet is derived from two words, robot and network, which literally means robot on the network,
just like a robot, follows the orders of a master botnet, follow the instruction of a master computer
called as command and control.
These botnets, also referred to as zombie computers, are often used to launch attacks on other targets.
Rootkits, rootkits infects the device drivers like audio drivers or network drivers or video drivers
because drivers run even before the operating system is booted.
It is usually difficult to detect a rootkit because antivirus only starts after the operating system
is booted up.
Key logger, a key logger is a type of spyware specifically designed to capture keystrokes of an infected
computer.
These recorded keystrokes are later sent to an attacker.
Another type of malware is a scareware this type is usually designed to trick the user into buying unnecessary
software like a fake antivirus program or sometimes more dangerous software.
Logic bomb, logic bomb is a malicious piece of code that will trigger when a specific condition is met,
like start doing a SYN flood attack on a company, ABC, exactly midnight of 25th December 2021.
or if my name does not appear in the payroll for three consecutive months, then
delete some data.
Backdoors, backdoors allow an attacker to gain unauthorized access to a victim's computer.
These malware are sometimes referred to as RAT's. Remote Access Trojans.
These compromised machines can be used to launch attacks on the other systems or they might be used to do
internal reconnaissance in a company's network.
It is important to understand that a malware in reality is usually built using behaviors of different
types of malwares, that is, you cannot clearly categorize any malware into one specific category.
To make this point more clear, let us look at an example of a ransomware.
Obviously, because it is a ransomware, a part of the code needs to take care of encrypting the file
on the infected machine.
This makes the malware ransomware.
However, the attacker might want this malware to spread to as many machines as possible so there will
be part of the code that will replicate the malware, making it a worm.
attacker might want to keep connection with the compromised machine, either to pass the decryption
keys or any other instructions.
So a part of the code keeps connecting to attackers machine, making this malware a botnet.
Finally, the attacker might package this whole malware into a wallpaper or a legitimate sounding software
like registry cleaner or speed booster, etc., thus making this program a Trojan.
So even though theoretically we learn different types of malware, in reality, they usually appear
as a combination of malware types.