Malware File Sizes
Virus File Size Distributions
Check the File Size

Viruses are very tiny programs. Our research shows viruses average 1MB in size, with 30% of viruses less than 200kB. The reason these files are so small is for speed … small files load in a flash, too quickly for the user to realize he or she has made a mistake and stop the download.

Here’s how we use the small file size against the virus makers: Virus writers use the product and file names to try and fool us into thinking they are legitimate programs. But closer analysis shows that legitimate programs of that product name would be one to two orders of magnitudes larger than a virus. For example, iTunes updates are usually more than 100MB. So PC Matic will check a file called “iTunes” against the expected size of that file and send up a red flag if the file appears to be too small for its name.

Speaking of names, our cloud-based system also maintains a list of favorite virus names. Read more.