I heard from some techie person that
.zip files never get infected by viruses.
Is this true? If yes, then why such behavior?
What they probably meant to say was that if a virus is in an archive, it cannot do any damage. This is because it is not running, and can't run, until it is extracted. This security benefit goes away if a user unzips it.
It is no more safe in reality though, than any other file on your computer that you are not clicking on.
EDIT: If it was automatically safe, that would be the best anti-virus program in the world.
Typical viruses usually append themselves to executable files, so that they themselves get loaded into memory. They will then spread to other executable file to increase their chance of getting loaded and spread.
Archives (zip, rar, etc) dont get infected as they arent executed. However, archives are an extremely common way to spread infected executables.
There may be viruses that specifically target archives, such as zip and rar. I dont think your "techie person" can say that so matter of factly. More than likely, he doesnt know what he is talking about, or just said that to give you an answer.
I think what that techie person was trying to say is this:
When a file inside an archive is modified, the archiver (let's say WinRAR) will ask you if you want to update the archive.
So, you run an EXE wich is inside of an archive, on an infected computer. During this process, the EXE file will be extracted to Windows's temp folder and let's suppose that the virus will infect it. When you close the archive that's when you will be asked if you want to update the archive, because the file was modified.
IMPORTANT: keep in mind also that if the EXE I gaved as an example, has a configuration file that resides in the same folder you maybe also be asked the same question, because after extraction and execution the program will try to save it's configuration file.
You can test this for yourself, for example:
Archive a text document, then open this document inside the archive and edit it. Then close the archive.
I must say that an archive is the perfect antivirus! I've been using it for years along with common sense, and I never had a problem.
If you keep all your files archived, then you can rest assured that viruses ar a thing of the past because even if they infect your computer you just reinstall Windows and forget about it.
I personally prefer to reinstall Windows (depending on your skills and PC, it can take 30' up to 3-4h for all the programs) rather than to have my PC run with an AV scanning all the time, slowing everything down.
Most PC users should be fine using common sense. Common sense is the first sense in user privacy and security, second is WinRAR and the rest is history :D
If I were to develop an AV it would be the first true AV ever created :)) it would be ONE eyed :)) and see everything, viruses would have no place to be =)) LOL I'm damn funny hahaha