computer virus- a piece of code that is capable of copying itself and typically has a detrimental effect, such as corrupting the system or destroying data
spyware- software that self-installs on computers and tracks the user's Internet use, mainly for marketing purposes
phishing- the activity of defrauding an online account holder of financial information by posing as a legitimate company
encryption- to convert (information or data) into a cipher or code, esp. to prevent unauthorized access
I used the Dictionary application for Mac OS to find all of the definitions here.