A file-infecting virus is a type of malware that infects executable files with the intent to cause permanent damage or make them unusable. A file-infecting virus overwrites code or inserts infected code into a executable file. This type of virus can infect a number of operating systems, including Macintosh, Windows and Unix.
A file-infecting virus may also be known as a file injector.
Techopedia explains File-Infecting Virus
A file-infecting virus is one of the most common types of virus. Typically, it infects files with .exe or .com extensions. When the infected file is accessed or executed, it may be partially or completely overwritten by the virus. A file-infecting virus can also spread across the system and over the network to infect other systems. Moreover, a severe form of file-infecting virus can also completely reformat a hard drive. Win32.Sality.BK is a popular file-infecting virus that was among the top 10 malware infections in 2011 and 2012.