How do viruses attach themselves to files?

Question

What does it actually mean when viruses "attach themselves" to files? By files I mean both personal files and system files.

Answer 1

They stay in memory and hook into the file open functions of the operation system (or in case of Word worms, into the document template's OpenFile function), actually intercepts the call to open a file, usually EXE files. The file is first opened by the virus, which simply adds itself to the end of the file, then modifies the header, so that the program actually STARTS by loading the virus then the virus passes back control to the program itself. THEN control is passed back to the operating system, which then opens the program normally, but the program was taken over... So the virus loads into memory (but usually, it sees itself in memory, and stops) then the program loads normally.

So the infect program, if put on some other computer and run, will infect the other computer.

Word worms behave similarly: by infecting the FileOpen function of the master template, it adds worm code to EVERY document you create, and by sending infected documents to others, the infection will spread.

Well, that's the short version. :)

Answer 2

2

Answer 3

executable files(files that run) basicly the virus adds it;s code to the file in the data area of the file and using special formatted data can get yous system to run the code....

personal files are diffren, you probably mean word processing files, in that case it;s a macro virus same thing though, it adds its own code to the file and when you run or access it the code runs...

Answer 4

Ever take biology?

Computer viruses are similar to actual viruses as they will add themselves to certain files to help them execute their payload. A real virus uses other cells to help it reproduce.

Really, it just gives the virus a way to spread itself and to be able to stay unnoticed.

Answer 5

You should ask that virus developer.