How to restrict users from uploading malicious files(exe, dll,etc) & limit file size in a webform

Hello, please i have a file atachment field in a form on my site. I want to restrict the size of the file that can be uploaded and the type. It's a vacancy page and I want candidates to only upload doc and pdf files. I want to also limit the file size to 50mb only. How can this be done within the BC system.

Thanks.