Our site had this warning The Site ahead contains Malware Warning. We created brand new site on different server on a completely different hosting and the pointed the domain to the new server.
Nothing from previous server was moved to new hosting. Its more than 6 weeks now. Warning is still there. We also contacted our domain registrar, they replied : Its not their fault and they can't really help us.
We've tried all the instruction that we found on internet.
I have the same problem before.
Some hacker add backdoor or spam script or autospam, autoemail software on your website or server.
Make a clean re-install for your server. and maker a clean re-upload your website.
When all done, install a anti-virus software for server if possible.
I assume this is the Chrome browser warning. If you have not created a webmaster tools account, do so now.
Once created, go to the search console (after adding the site to your account and verify ownership) by uploading a file given by Google to your sites root folder. Also, add a sitemap, if possible and submit the site to index.
Once that is done, apply for a "Reconsideration Request". It can take up to a week but that is much faster than just hoping it goes away.
I also got similar warning when visiting one of the page on my site. I have troubleshooted the problem and found the reason - the product I promoted somehow as identified as a malicious program. I didn't know how it happened. Finally, I deleted the page and the problem was solved. So, do you promote any potentially dangerous program on your website? If not, your website might be attacked by some malware. Try run a malware scanner to detect and remove it.