What type of virus is stored in the first sector of a hard drive and is hard to detect?

A Boot Sector Virus is a type of malware that targets the boot sector of a hard drive, which is the first sector that the computer reads when it starts up. This makes it particularly insidious because it can execute before the operating system is fully loaded, allowing it to evade many security measures and antivirus programs that run within the OS.

Because it resides in an area that is often protected or not frequently checked by standard antivirus programs, detecting a boot sector virus can be quite challenging. Moreover, once it infects a system, it can spread to other devices through removable media or network installations, making its impact quite far-reaching.

The other options refer to different types of malware. File viruses attach themselves to executable files, program viruses insert themselves into other programs, and polymorphic viruses change their code to evade detection, but none of these specifically target the boot sector in the way that a boot sector virus does. This distinct behavior highlights the unique nature of boot sector viruses, confirming why they are known for their difficulty in detection.