##Terminology

Malware is a broad term that includes any soft<i>ware</i> which performs <i>mal</i>icious actions. There are several common names for various classes of malware. The specific definitions often change over time, as is the case with the term "virus". Common definitions for various forms of malware are:

* Viruses modify existing programs, "infecting" them so their execution also triggers the spread of the virus, until the computer is entirely filled up with maliciously modified software. True viruses are fairly rare now days, but the term continues to be used synonymously with malware.
* Trojans disguise themselves as harmless programs, such as video games or screen savers. They require user interaction to execute. These are common in torrents.
* Worms spread by themselves through the network, often by exploiting software vulnerabilities in networking services. A worm that exploits popular software can spread extremely rapidly.
* Rootkits are self-hiding privilege escalation toolkits. They are designed to embed themselves in a system with a high privilege level, ensuring that nothing that runs on the computer can detect it. Rootkits are often able to completely evade antivirus software.
* Ransomware is old, but has gained popularity recently. Simple ransomware simply locks the victim's computer until a ransom is paid. More modern and sophisticated ransomware actually encrypts files and refuses to decrypt until a ransom is paid. These programs often make little effort to avoid removal, as their job is done as soon as they execute for the first time.
* Spyware is any class of malicious software that monitors a user's private activities and reports it back to the owner of the spyware. It can be used by anyone from stalkers to identity thieves.
* Adware is among the least harmful forms of malware. Adware includes any software that displays or injects advertisements on a computer. It is considered malicious when it is installed without consent, or makes attempts to avoid removal. It is commonly implemented as browser. toolbars.

Malware can belong to multiple classes. A program that spreads over the network and embeds itself in the kernel for persistence would be both a worm and a rootkit, for example.

##Exploits vs executables

Exploits are not malicious. An exploit is anything that attempts to utilize a security vulnerability to violate the confidentiality, integrity, or availability of a service or task. Sophisticated malware, especially worms, may contain exploits to break security barriers to spread. However, all malware would fall under the classification of executables (or at least executable code, as in the case of shellcode which is not an executable file by itself, but rather is injected into a running process to change its behavior).

What you appear to be describing is the difference between a worm or browser exploit (able to spread with no or little interaction), and a trojan (requires user interaction to trigger infection).