Home > Threat descriptions >

EXE infector

Classification

Category: Malware

Type: -

Aliases: EXE infector, EXE infector, EXE virus

Summary


EXE Infector (generic description).

This type of virus infects EXE files. An EXE file is a binary executable file. EXE files can be 16-bit and 32-bit. 16-bit executable files contain for 16-bit operating systems such as DOS and Windows 3.xx. The 32-bit executable files are used in modern operating systems such as Windows. Both 16-bit and 32-bit executable files have headers. A header is a data area that preceedes an executable code and contains vital information about a file (for example all headers contain entry point addresses - the place where execution of a file starts).

Removal


Automatic action

Based on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the detected program or file, or ask you for a desired action.

Knowledge Base

Find the latest advice in our Community Knowledge Base.

About the product

See the manual for your F-Secure product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details


An EXE infector can be prepending (writes itself before the original file), appending (writes itself to the end of the original file), overwriting (overwrites the original file with its own code), inserting (inserts itself into gaps inside the original file), companion (renames the original file and writes itself with the original file's name) and cavity infector (writes itself between file sections of 32-bit file). An EXE infector can be memory resident and non-memory resident. Memory resident viruses stay active in memory, trap one or more system functions (usually interrupt 21h or Windows file system hooks) and infect files while they are accessed. Non-memory resident viruses search for EXE files on a hard disk and infect them.

An EXE infector can be non-encrypted, encrypted or polymorphic. An encrypted or polymorphic virus consists of one or more decryptors and a main code. A decryptor decrypts main virus code before it could be started. Encrypted viruses usually use fixed or variable key decryptors while polymorphic viruses have decryptors that are randomly generated from processor instructions and contain a lot of commands that are not used in decryption process.