Because Mudcat doesn't have images and fancy downloadable files, the security is fairly low. Nothing to download that has noxious things hidden inside. But the ads that load come from Google, and who knows what comes through. You can express preferences on ads (that's a different operation, probably achieved by visiting a Google ad preference site.) The security caution I usually see on my Windows computer has to do with searching the DT, where there is less security or certificate activity than the rest of the site. I just click past it.