The actual scam of fake security alerts doesn't actually do anything other than but out the bait, e.g. your system is infected/vulnerable, etc. inviting you to visit a site and or run a scan. It is at that point that you are likely to become properly infected or asked for payment.
avast does pick up on some of these but they are constantly changing, send the sysguard.exe to avast for analysis, so it might be added.
Send the sample to
virus@avast.com zipped and password protected with the password in email body, a link to this topic might help and false positive/undetected malware in the subject.
Or you can also add the file to the User Files (File, Add) section of the avast chest (if it isn't already there) where it can do no harm and send it from there.
A copy of the file/s will remain in the original location, so you will need to take further action and can remove/rename that.
Send it from the User Files section of the chest (select the file, right click, email to Alwil Software). It will be uploaded (not actually emailed) to avast when the next avast auto (or manual) update is done.
After you have sent the sample.
If you haven't already got this software (freeware), download, install, update and run it,
preferably in safe mode and report the findings (it should product a log file).
