can a virus execute by itself?

[Richard20]

Is there any type of viruses can execute by itself after download then on the HDD without clicking on it??

if there is ..... can you refer me to any sites about them?

[SuperDave]

Computer viruses are not very common these days because there's no money in it. You're more apt to get Ransomeware or Adware on your computer. However, you can get a lot of information here.

[johnshelbyy]

Is there any type of viruses can execute by itself after download then on the HDD without clicking on it??

if there is ..... can you refer me to any sites about them?

I think it's more accurate to say 'a virus can't execute itself, unless it has the cooperation of the Operating System and/or software bugs and/or the user.

If the OS allows files to be executed automatically because of their name or location (for example an email attachment) then a virus can masquerade as a legitimate file and be executed by the OS without user intervention. This used to be the default behaviour in early email clients.

Also, if the OS or specific software has errors that a virus can exploit to run its code, then a virus can start itself.

But users are most often the means for a file to be executed. I was surprised recently when a work-colleage told me she thought her computer had a virus after she opened an attachment in an email from a complete stranger. I thought she would have known better.