I often use older software because I need it for specific work, but Avast keeps blocking it and calling them viruses. How do I update it to stop doing that?
You will have to add those programs to the Exclusion list. To do this, Go to Settings > General and scroll down to expand Exclusions section. Use the tabs to navigate to the correct item category you want to exclude. Choose Programs and then add the files there. Avast won’t scan them at all until you remove the entries, even if you update or start on-demand scanners.
To find more about it, use the following support page: https://www.avast.com/en-us/faq.php?article=AVKB168#artTitle