I don't have an active antivirus anymore, just a firewall. It's useful to have the scanner there for when I'm not sure if a program's safe or not.
Here's my advice if anyone wants it.
There are three main ways of getting a virus:
- Download a malicious program and run it.
- Run a badly written program which opens an infected document. IE for example used to have a bug where the VBScript engine used a fixed size string buffer for one of its commands. Hackers could intentionally use longer strings which contained machine code. The buffer was allocated on the stack, so when it overflowed it overwrote the return address causing the CPU to start executing code in the string.
- Use an infected USB stick, floppy disk, CD or DVD.
The easiest way to stop the first one is to make sure you are downloading from a well known site, and if you are in any doubt, try googling the name of the program and website to see if there are any complaints. There is also the possibility of accidentally running a program. To stop this, make sure explorer is set to always show extensions on files, and it should be immediately obvious if something is a program. Without this a file named "a.jpg.exe" will show up as "a.jpg" and so you might think it's safe to open.
The second one is hardest to stop. Luckily very few programs are this bad any more. IE with default settings, firefox and chrome are all completely safe to use, and you can do the same as for the first method for other programs.
The third one can mostly be stopped by disabling auto-run. Try not to run programs from portable storage at all if possible.
Documents are completely safe to open, as long as the program used to open them is security conscious.
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