Hello!
I’m wondering about two things:
Can I get infected just from downloading a bad file from the net (eg.: file.exe) to my hard drive, or do I have to run in to get infected?
The malware that automatically downloads from bad sites - it also automatically runs and infects the PC too, am I right?
Thank you for the answers in advance! 
Hi Bellzemos,
Viruses can be transmitted in various ways so also in a downloaded file. The immediate source of the downloaded file is usually unaware that it contains a virus. Some viruses wreak their effect as soon as their code is executed; other viruses lie dormant until circumstances cause their code to be executed by the computer. Some viruses are benign or playful in intent and effect (“Happy Birthday, Bellzemos!”) and some can be quite harmful, erasing data or causing your hard disk to require reformatting. A virus that replicates itself by resending itself also as part of a network message is known as a worm.
A specific form of these viruses are File infectors, and some can be quite catastrophic like virut for instance, ruining the whole OS until a complete reinstall becomes inevitable.
File infectors. Some file infector viruses attach themselves to program files, usually selected .COM or .EXE files. Some can infect any program for which execution is requested, including .SYS, .OVL, .PRG, and .MNU files. When the program is loaded, the virus is loaded as well. Other file infector viruses arrive as wholly-contained programs or scripts,
polonus
Thank you for all the information, Polonus. Can you answer me this too, please:
Let’s say that I downloaded an infected file called “badfile.exe” from some site.
If I delete this file, without running it, will it infect my system?
I know that it will infect it if I click on it (run it), but if I only download it and then find out that it’s a virus and delete it - it won’t infect my system, right?
Thanx again!
Anyone, please?
If ‘you’ (and not a drive by exploit) downloaded an infected file using the save as method then it wouldn’t be run.
The problem being clicking on a link to download a file could also activate another process to take advantage of some security vulnerability to subsequently silently install the file, after all that is what malware does.
Visit an infected/hacked web site and it could be trying to run malware which depending on your security could easily install malware.
So there really is no way to answer this accurately for a given situation without full information. Since you are speaking hypothetically and not specifically then the answer would have to be yes it is possible.
Yes, it’s just a hypotetical question. Let’s say I downloaded something via save-as way and the file is on my hard disk. But I didn’t run it, and the download link was clean and OK (not redirecting me anywhere). I’m not infected until I run that file, am I correct? Thank you!
I simply can’t say with any certainty as there are still parameters as I mentioned earlier that could get you infected, even if ‘you’ initiated the download.
Nothing in life is 100% (other than death and taxes) and this is no different, but generally a manually initiated save as download would be inert unless run. Unfortunately, there are methods of exploiting this to run/install it silently so there really can be no guarantees.
OK, thank you!
You’re welcome.