Here are some important steps to efficiently fight cross-site contamination:
1. Backup. Make a list with all your important sites and backup everything to prevent data loss.
2. Better hosting. Contact your hosting provider and ask for a solution to address the cross-site contamination.
They should provide better hosting ( reseller hosting plan, VPS, etc ).
For two or more sites, we recommend getting a reseller plan from Stablehost, Hawkhost, Crocweb, Krystal or Crucial.
If you need more resources, a Knownhost managed VPS could work.
3. Damage analysis. Run tools like virustotal, sitecheck, mx blacklist to notice if domains are blacklisted. Also run “site:domain.com” on Google – replacing domain.com with your own name. This way you’ll notice if site is affected by SEO spam.
4. Malware cleanup. Make sure you clean every website before you perform a migration to a safer environment. Ideally updates should be applied and traffic filtered using a WAF.
5. Blacklist removal. Notable blacklists are currently provided by McAfee, Norton, Google Ads, Google search console and ESET. After a cleanup is successfully completed, blacklist issue should be addressed to prevent a further traffic drop.
Notes:
a) Make sure your sites are proper isolated after you’ll get better hosting.