This question is meant to ask for general guidance - although I will mention a specific example. (It is not my intention to call out a specific user - simply the issue is better explained on an example.)

I have noticed a domain which has several links on Stack Exchange ([28 posts](https://stackoverflow.com/search?tab=active&q=url%3a%22%2Abillthelizard.com%2A%22) on Stack Overflow and [34 links](https://stackexchange.com/search?q=url%3a%22%2Abillthelizard.com%2A%22&pagesize=50) networkwide.) 
When trying some of those links I got the warning:

> Threat found
> This web page may contain dangerous content that can provide remote access to an infected device, leak sensitive data from the device or harm the targeted device.
> Threat: JS/Redirector.PSC

Google diagnostic tool [run on this domain](https://transparencyreport.google.com/safe-browsing/search?url=billthelizard.com) says: "Some pages on this site are unsafe
The site contains harmful content, including pages that: Try to trick visitors into sharing personal info or downloading software."

It seems likely that the domain worked in the past. (I managed to find Wayback Machine links for some of those posts. In fact, in some cases [those links have already been edited](https://stackexchange.com/search?q=url%3a%22%2Aweb.archive.org%2Abillthelizard.com%2A%22&pagesize=50). And some of them have been replaced by a link [to a new domain](https://stackexchange.com/search?q=url%3a%22%2Abillthelizard.blogspot.com%2A%22&pagesize=50).) But after the domain expired, somebody else used the same domain and placed some harmful content there

What should be done in situations like this?

 * Should I try to replace the links by the Wayback Machine links, if they are available? (Or a link to some new domain, if it is possible to find whether the original content was moved elsewhere.)
 * What should be done if there isn't some suitable replacement for the link?
 * If some site has many such links, should I notify the mods? Should I mention this on the per-site-meta?
 * In the cases of locked posts, the only reasonable option I was able to think of was flagging for moderators' attention.
 
In this case I have option to notify the owner of the domain - the user seems to be still active on Stack Overflow. But in other similar cases, there might be no such possibility.

I found a related discussion on Meta Stack Overflow: [How should questions that contain links to an infected/virus page be flagged?](https://meta.stackoverflow.com/q/293973) But that one seems to be mainly the discussion of a specific flag on one particular post.