In that case, it probably is not a virus. It is probably malware.
Nowadays these are practically synonyms,
No, they aren't.
To add to this, a virus is a piece of malware but a piece of malware may not always be a virus. There are other categories such as trojans that cause issues with computers and enter them the same way viruses do.
that case, it probably is not a virus. It is
and antiviruses detect both.
Anti-virus software may try to detect some malware, but it would be impossible for it to detect all malware.
Most wide-spread malware is protected by antivirus software. There are software that antivirus doesn't trust like some antiviruses don't trust the Bitcoin Core wallet for example.
Antiviruses measure familiarity with code and how widespread it is to determine its safety (signatures used to generate the code are also checked). Higher level languages are not checked as easily by AV software as lower level/intermediate languages are and therefore, getting a piece of software that is cleared by AV to run another piece of software/code that isn't can be a main producer of issues.
It is tough to know if your new wallet is compromised or not... you should completely refresh the entire system or reinstallation process.
That's a good suggestion, the disk needs the operating system completely uninstalling and anything else on the disk completely removed. Then the operating system can be reinstalled and tested with smaller amounts.
I would say @OP as this issue has happened to you once, if you stick with Bitcoin, try and change the way you surf the web or change how you store you coins.
The coins seem to have finished up in this address: 1Kefz6BcNjK6MhTrLnr2KAQq8KyPNCeMSS
Keep track of that OP and see if the coins move anywhere else after that (though that might take a while).