Viruses are the common cold of computers: easily spread and often misdiagnosed. The word “virus” is frequently misused in describing other forms of malware. Actual viruses are a small bit of executable code that spreads when users open infected files or applications. A few viruses that affect Mac OS X have been found, and Mac users can also inadvertently spread Windows viruses by passing along infected files.
A Trojan horse is like the college roommate that seems cool until they stop paying rent, eat your food and leave dirty clothes everywhere. It enters under the pretense of usefulness but actually contains malicious code. Several Trojan horses affect Mac OS X, most notably the Flashback Trojan.
Worms are like the elusive varmint scurrying through the insulation in your wall. Because they don’t need to attach themselves to an existing file or program, they can be very difficult to find. A type of virus, worms spread over networks, and can carry out malicious actions once they find new hosts.
Spyware is like the creepy neighbor that stares in your window and shuffles through your mail. It enters your Mac as a Trojan horse and then secretly monitors your computing behavior, collecting personal information such as surfing habits and web sites you’ve visited.
A botnet is like an army of zombie computers bent on destruction. Your Mac could be forced to join the zombie army as a consequence of a malware attack. The network of compromised computers is then used to send spam or to attack other computers.
Spam is the mosquito of the computer world: annoying and ubiquitous. A single spam message can be dealt with easily enough, but en masse it can crowd your inbox and cause a significant loss of productivity.
An exploit is like a schoolyard bully that zeroes in on your weaknesses. It’s a piece of software, a chunk of data, or a sequence of commands that takes advantage of a bug, glitch or vulnerability in order to break through your Mac’s security defenses.