As an IT Security Consultant I have observed there are many reasons for the spread of viruses and malware across the Internet. The primary reason is the lack of security on machines connected to the Internet, let me explain. There are two divisions here, the first being systems owned by medium to large businesses and the second being small office and home systems. The security difference between the two is radically different. As a whole the larger organizations have much better security.

There are several reasons for this. First and foremost these organizations have learned through painful experience the cost of not being secure. They realize that although security can be expensive it is much more expensive to be insecure. The larger companies for the most part now implement corporate controlled antivirus, antispyware and antispam software that scans for viruses, adware, spam and spyware as traffic enters the network. This way the malware are caught before they ever reach the users PC. The PCs themselves will also run client versions of things like Norton Antivirus Corporate Edition which are continually scanning the PCs for any viruses or other malware that may have been introduced to the PC directly by the user.

The larger companies also have multiple layers of Firewalls and Intrusion Detection Systems guarding their networks. While the average large company has pretty good security most computers in small office and homes have poor security. Many if they even have antivirus software do not update it. Very few if any will have antispam, antispyware or antiadware software. So they literally have no protection against viruses, adware, spyware or spam. Because many of these devices which make up a large percentage of the devices on the Internet do not have protection they are usually infected by every type of malware and because of the viral nature of malware they spread it to any PCs that they have access to.

For example friends, relatives, business associates etc. who are also not likely to be protected and then pass the virus or other malware on to anyone they have access to and the cycle continues exponentially until within a few days it