Linking to bad, broken & malware infected sites can make your site bad too, for visitors & for SEO.
But how do you know you're not linking to bad sites? By using the Link Scanner.

Link Scanner is a unique SaaS tools that's a part of WP 301 Redirects PRO plugin. It'll help you to:

scan every single link on your site; in posts, pages, CPTs, widgets, header, footers - everywhere
detect links that are broken & easily fix them
detect links to pornographic sites, those infected by malware or phishing sites
check links with Google Safe Browing API
see rel, target and other link attributes in one place
get additional data on every link such as the quality of the site it links to
run automatic scans so you always have fresh data
scans are done externally by our SaaS so they don't put a strain on your server