How come viruses work?

**AtW** · 11 November 2009, 14:06

Originally posted by Tarquin Farquhar View Post

browse the web

And the virus wants to browse your online bank account...

**DaveB** · 11 November 2009, 14:07

Originally posted by Tarquin Farquhar View Post

Pardon me for asking a stupid question, but should it not be possible to set up your PC so that it will do the things that you want to do but will not do the things that viruses want to do? Or at least not without the OS (not the virus) asking you if you want to do it first?

I want to read and send email, browse the web, read and write documents and spreadsheets, listen to music, touch up photos. Can't I do that on a PC that an incoming email or a duff website simply can not screw up?

You can do that on any PC, just don't install windows on it.

**RichardCranium** · 11 November 2009, 14:09

Originally posted by Tarquin Farquhar View Post

How come viruses work?

Because Microsoft doesn't write them.

**NickFitz** · 11 November 2009, 14:38

The system doesn't know what the software wants to do until it's done it, by which time it's too late. It's mathematically provable that static analysis of executable code cannot determine the consequences of executing that code for all possible executables and inputs.

Otherwise we could solve the Halting Problem, but we can't, although we can prove that we can't.

**northernladuk** · 11 November 2009, 14:48

Your not thinking about this one.

Go back to basics.. What is a virus... its a program that does stuff on your PC just like OUtlook, Explorer etc. The problem is to differentiate which programs you want to run and which you don't. Anti viri software does this but it is a race. The clever bit is how to get it past that and on to your PC and run. After that its just a normal program like the ones you are already running.

There are so many you just can't say don't do this cause they will find one that will do somethign else instead. How does your pc know that you want to send email or to hack a website. It doesn't so it just runs it happily either way.

**VectraMan** · 11 November 2009, 14:48

Originally posted by DaveB View Post

You can do that on any PC, just don't install Firefox on it.

Fixed that for you.

http://www.internetnews.com/software...le.php/3847461

**NickFitz** · 11 November 2009, 14:51

Originally posted by VectraMan View Post

Fixed that for you.

http://www.internetnews.com/software...le.php/3847461

Unfortunately, that study is so seriously flawed as to be meaningless.

**RichardCranium** · 11 November 2009, 14:59

I can't be bothered writing full explanation (I've got to go and sign on in 40 minutes) but essentially it is because Windows is NOT an operating system, it is a program laucnher.

Us old farts with bald heads or grey beards remember real computers with multi-processors and multi-threading and multi-user and real concurrency and ... security.

Amongst the many activities of a real operating system are to protect the machine from the programmes running on it, and the programme areas from one another. On a real computer you cannot scribble all over the RAM with any old tulip like you can on a Micro$oft box. Your programme can screw itself all it likes but it will not have the permissions to change (or even see) anything else.

Imagine every thing running on your PC as running on its own virtual machine. A bit like that. Except the disk space is protected too. And better. And without the degradation.

But apparently PCs were better than Big Iron.

**Tarquin Farquhar** · 11 November 2009, 15:22

Originally posted by RichardCranium View Post

I can't be bothered writing full explanation (I've got to go and sign on in 40 minutes) but essentially it is because Windows is NOT an operating system, it is a program laucnher.

Us old farts with bald heads or grey beards remember real computers with multi-processors and multi-threading and multi-user and real concurrency and ... security.

Amongst the many activities of a real operating system are to protect the machine from the programmes running on it, and the programme areas from one another. On a real computer you cannot scribble all over the RAM with any old tulip like you can on a Micro$oft box. Your programme can screw itself all it likes but it will not have the permissions to change (or even see) anything else.

Imagine every thing running on your PC as running on its own virtual machine. A bit like that. Except the disk space is protected too. And better. And without the degradation.

But apparently PCs were better than Big Iron.

Well, I'm an old Big Iron guy myself, and I used to work on mainframes. Is it related to the fact that on a mainframe you basically can't browse around idly, you have to know what you want to do?

Is it helpful to create a rather powerless account and use that normally? Or do the bad guys just hijack the powers of bits of the system that are running as God?

Is it helpful to run unix/linux/OSX instead? Or should I go farther and run in a virtual machine? Or is that pointless because the virtual machine software itself has the power to screw things up?

How come viruses work?