How Viruses Work: A virus, in most cases, tries to accomplish one of two things: render your system inoperable or spread to other systems.
Many viruses will spread to other systems given the chance and then render your system unusable. This is common with many of the newer viruses.
If your system is infected, the virus may try to attack itself to every file in your system and spread each time you send a file or document to other users. Below it shows the virus spreading from an infected system, either through a network or by removable media.
When you give removable media to another user or put it into another system, you then infect that system with the virus.
Below: Virus spreading from an infected system using the network or removable media.
Many viruses spread using email. The infected system attaches a file to any email that you send to anther user.
The recipient opens the file, thinking it’s something you legitimately sent them. When they open the file, the viruses infect the target system.
The virus turn infects the recipient of the email. Below we show you how a virus can spread from a single user to literally thousands of users in a very short time using email.
Below: An email virus spreading geometrically to other users.
Quite a few of the newer viruses spread through USB thumb drives. An employee may see one lying about and plug it into a machine without realizing that it might contain a virus. This is such a problem that the Department of Defense has banned the use of thumb drives.
NOTE: For more information on thumb drives and viruses, see www.tomshardware.com/news/usb-flash-virus-secure,6564.html