This error is most commonly seen when your anti-virus software mistakenly reports game files as malicious and quarantines them.
There are a couple of ways to resolve this:
within the anti-virus software look for game files that have been reported and mark them as safe
set your anti-virus software to Game Mode
have the anti-virus software exclude that game folder when it scans for malicious content. Here's how to do that with popular anti-virus software.
You should also temporarily uninstall any applications listed in our Programs Which May Interfere with Steam.