[7] The virus actually spread farther than the brothers had intended,[4] The University of Maryland (others say Delaware[10]) discovered the virus was present in the US (on October 22nd, 1987[11]),[12] and that it had spread to thousands of machines (20,000[13]—250,000[14][15]). Initially, the brothers were simply curious about how IBM DOS worked, and wanted to experiment with it; "We were experimenting with a few things. One thing was whether in DOS we can have multitasking...[t]he DOS was something new and when we explored the security issues of DOS [we] realized it was possible [to infiltrate] it with a piece of code...[We wanted] to find out how the floppies and how the programs and software move around...[w]e [could] see and watch whether it’s going to spread around the world or remain within a certain group of people".[16] The virus was designed in an extremely clever way; normally, the virus would be too large to fit into the boot sector (and in fact if it is loaded into the boot sector it would take up it's entire memory and more, which would therefore make it impossible to run).[17] The brothers designed the virus in such a way as to store the first 512 bytes in the boot sector, and then store the rest of the code, along with the remaining virus code in six different portions of the floppy disk.[17] The location of the virus can be found at cylinder 0, head 0, sector 1 ; the first sector on the disk.[17] When it is found by the computer, the executable functions io.sys , command.com , config.sys and autoexec.bat are loaded.[17] However, it was not until a few years ago that the virus was rendered completely harmless.[7][n. 5] This was only ever possible because of the change in 5.25 inch floppy disks to 3.5 inch floppy disks.[7] Aryeh Goretsky, who is a personal friend of John McAfee of McAfee Antivirus company, had his first contact with Brain when he worked as a technical support engineer; it was his first assignment within his designated role. In this way, Brain was the first reported virus that fit into the definition of harmful.The virus actually spread farther than the brothers had intended,The University of Maryland (others say Delaware) discovered the virus was present in the US (on October 22nd, 1987),and that it had spread to thousands of machines (20,000—250,000). Initially, the brothers were simply curious about how IBM DOS worked, and wanted to experiment with it;The virus was designed in an extremely clever way; normally, the virus would be too large to fit into the boot sector (and in fact if it is loaded into the boot sector it would take up it's entire memory and more, which would therefore make it impossible to run).The brothers designed the virus in such a way as to store the first 512 bytes in the boot sector, and then store the rest of the code, along with the remaining virus code in six different portions of the floppy disk.The location of the virus can be found at; the first sector on the disk.When it is found by the computer, the executable functionsandare loaded.However, it was not until a few years ago that the virus was rendered completely harmless.This was only ever possible because of the change in 5.25 inch floppy disks to 3.5 inch floppy disks.Aryeh Goretsky, who is a personal friend of John McAfee of McAfee Antivirus company, had his first contact with Brain when he worked as a technical support engineer; it was his first assignment within his designated role.

Mikko Hypponen traced the origins of Brain to Pakistan and visited the brothers who reside in the same residence they wrote the code in.