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Protect Your Computer - Beware of Dangerous File Extensions - Part 4

Back on May 4, 2000, one of the most damaging viruses ever created was launched and believed to have initiated in the Philippines. The ILOVEYOU virus was estimated to have crippled 10% of the entire population of computers connected to the Internet during that time and caused an estimated $5.5 Billion in damage throughout the world. The worm was written in Visual Basic Script with file extension VBS, a common file extension used by most harmful programs in circulation over the Internet today. It became the benchmark of modern worms written in VBScript and distributed through email.

The virus requires the end user to run the script to deliver its payload. Those unfamiliar with the effects of running files with VBS extension were the first to experience the infection. As part of its design, the virus renamed several files of a computer appending the *.VBS extension to their original filenames.

While DOC and XLS file extensions are very common to us, there is still a need for us to be vigilant when receiving these files. Other forms of virus, worms, and Trojans, hide themselves in documents through "MacroInstructions" or simply termed as "Macro". These forms of viruses work similar to those that are written with extensions EXE, COM, or VBS. They can execute similar commands and produce similar severity of damage.

For a macro virus to deliver its payload, the main application must be launched first. So, if you received a Word document from an email that has a DOC extension, then there is a big chance that it contains a macro virus. Opening the file will trigger the launch of the virus and start damaging your computer and propagate.