Where to find viruses

It is important to know where a virus can be ôhidden". The first thing that must be clear is that in order to carry out its work of infecting, or totally or partially damaging computer data, a virus must be executed. Thus, viruses will only insert themselves in areas where they can be executed:

• Executable files: viruses insert themselves in executable files in order to be able to control the computer.

• Documents of any program able to manage macros: traditionally, non-executable files could not contain viruses (or at least there wasn't a reason for them to contain viruses), since a virus in a non-executable file cannot do any work. However, due to the latest technical advances, certain programs such as the Microsoft Office suite have endowed non-executable files such as documents or spreadsheets with macros. A macro is a combination of instructions that can be executed by a certain program. In other words, a Microsoft Word document can contain a combination of instructions that Word itself will run. This has widened the possibility for viruses to infect files, which, despite being non-executable, contain macros.

• Files attached to e-mail messages: any type of file (executable or not) may be attached to an e-mail message. All e-mail messages, together with their corresponding attached files, are usually stored in one file. Since the structure of this file is not standard, nor does it have to be known, an antivirus may see such a message base as just another file and not find any viruses contained in it.

• Boot sector: the boot sector is an area in a diskette or hard disk containing important information on the type of disk. The boot sector also stores a program that is run when the disk in question is used for booting. Given that the program stored in the boot sector is able to run itself, it is also susceptible to being infected by a virus. You must bear in mind that a boot sector virus is also executed if an attempt to boot the computer from a diskette is made, whether or not it is a boot disk.

• Java Applets: before, Internet pages, or Websites (HTML pages), could only contain text or graphics. This has changed with the need to be able to create more complicated Web pages. Today, Web pages can also contain small programs called Java applets. When a browser downloads a Web page with some of these small programs, it makes sure to execute them. It works in a similar way as a macro document. For this reason, Java applets are also susceptible to being infected by viruses.

• ActiveX Controls: ActiveX controls have the same function as Java applets. For this reason and given that they are also executable, they are susceptible to being infected by viruses.

Panda Antivirus 6.0 is capable of scanning for viruses in any of the areas mentioned above, thus offering the highest levels of protection.