Malware is a generic term for all types of software that the bad guys use to attack your computer for their nefarious purposes. Some of these yo-yos are just pimply faced guys living in their mother’s basements trying to get creds with other hackers by bragging on their bulletin boards. Others want to take over your computer to send out spam email advertising Viagra, etc. or to be part of a bot-net (short for robot) which can be used in cyberattacks on some person of organization which has incurred their wrath. The most common type is the DDOS or Distributed Denial of Service attack where a bot-net is commanded to send large streams of pings or connect requests to the target site that legitimate users can’t get through. A third objective may be to make money. This can be by attempting to steal passwords and bank codes or by extortion.
One of the earliest types was the worm which propagates itself by capturing a machine, examining its contents and then uses what it found to attack the next machine.
Another type is the Trojan Horse. In this case you download something you want like a game or a screen saver and hidden in there is the gift that keeps on giving. The payload could be anything, but because you, in essence, invited it in there’s nothing that your anti-virus can do to prevent it.
If you have a Windows PC, you must have an effective anti-virus, anti-spyware package with a current license and an up-to-date set of virus definitions. MACs typically do not need an anti-virus program for three reasons. First, the underlyinf UNIX operating system on the MAC is inherently more secure than the Windows OS. Second MACs are 10% or less of the market. If you are going to spent the effort to create malware, are you going to shoot for 10% of the market or the other 90%. I rest my case. As in the situation with diseases i living things, a concentration of a single species leads to more opportunity for propagating disease, the same thing holds in computing systems. If every system is the same, it is easier to devise a way to take down many systems.
One of the first worms sent out on the internet was the Morris Worm of 1988. When this worm hit Bell Labs, we were totally unaffected. The worm carried some binary software (think DNA) that would only run on a certain variety of UNIX from Berkeley on DEC VAXes or Motorola 68000 series processors. Since we didn’t typically use there, the worm was stopped cold at our firewalls. Interestingly I worked with the originators father, Robert Morris, on a computer security task force at the Labs.