Malicious software can come in many forms and is commonly spread by email. What happens is that the malicious software scans the address book of the user on the affected machine, and sends messages to other users. When this message is opened by another user, the malware spreads. There is also a type of malware known as a Trojan horse, which poses as a legitimate application. In many cases, malicious software simply slows down the network the computer is on, in particular mail servers. Some, however, are more damaging: many an inadvertent malware software download has ended with a user losing some or all of the data on his or her machine.
Because the average user has no way of knowing when a malware software download has occurred, most use some type of antimalware software (commonly known as antivirus software), and regularly conduct virus scans. There are many, many types of antivirus software available that will remove malicious software, and there are both free and commercial packages. One of the most popular free packages is called AVG, which will conduct malicious software scans using up to date virus definition files. The most popular commercial software is Symantec antivirus, which covers all aspects of malicious software removal.
Virus scans are the most important part of malware prevention, and any antivirus software will have an update feature that will download the latest virus definitions files as new pieces of malicious software become known. After obtaining antimalware software, the first thing to do is update it and then do a full scan of the machine. If any virus infected files are found, they can hopefully be removed with little trouble.
The machine should be rebooted after a scan for malicious software, in order to prevent any malware on the machine from regenerating itself. One the computer has been rebooted, the most important element of virus protection to set up is a 'live scan' feature, whereby the application scans the computer's files in the background and looks for and removes a any malicious software it finds.
In recent years, the most common way for malware software to spread has been through email, and particularly with Microsoft outlook email software. Any good antivirus program will automatically scan any incoming and outgoing email for malware, and remove them automatically.
Once antivirus software has been properly set up, the whole process should be non-intrusive for the average PC user: the software will automatically update and scan the machine for malicious software in the background while the user is working. The one thing to keep in mind is the affect on system performance due to the background scanning, and users with older machines may find the Symantec background scan slows down their machine noticeably - AVG may be a better choice.
Whatever piece of anti malware software is installed, once it is properly set up the average user should have little to no problems detecting and removing a malicious piece of software. With the right malware software, most of the problems caused by malicious software and its removal have become easy to solve, so that the average user should have little to worry about when it comes to malicious software.