There is no conclusive response to this question as the most common type of malware differs depending on which region of the world you are situated in, and also alters in time. Some of the most common types of malware include viruses, worms, Trojan horses, and adware.
Viruses are one of the earliest and most common types of malware. Adware is a type of malware that displays advertising on a computer, frequently in a pop-up window.
Malware is constantly progressing, and brand-new types are continuously being created. https://gulfoilspillrecovery.org/?p=423 The types talked about above are some of the most common that you might encounter.