When you do google search to certain website or blog, google puts the warning flag in its search results for pages which to notify the surfers. Google users were redirected to page that warned: “This site may harm your computer.” The purpose of the warning is to help protect web surfers who are using Google search results.
1. Your site was hacked and this is the most common reason. Someone had modified files in your site and maybe put the injected code.
2. One of your backlink or website’s link is reported as a bad link or maybe having the malicious code.
When i opened my google webmaster tool, It shows “This site may be distributing malware.”
Problematic URLs shows that the websites has the suspected injected code.
Solutions and Actions:
1. Find and remove the suspected injected code in the website or blog.
2. After you have removed all harmful code from your site and addressed the underlying vulnerability that caused it to be compromised, you can request a review of your site from google webmaster tool.