Warning of potentially dangerous sites
Sometimes web resources contain malicious code along with useful information. Visiting these sites may infect your computer with viruses, as well as damage or steal your data.
To protect users, Yandex regularly checks indexed sites for malicious code. If such code is detected, a warning will be displayed in the snippet of the infected resource: “This site may harm your computer or mobile device”.
Yandex antivirus and Sophos® products are used to check pages.
We do not remove infected sites from search results because the site may contain unique useful information that is relevant to your query.
By going to such a site, you are exposing your computer or mobile device to risk. There is always the possibility that you won't catch a virus, because certain conditions are often required to execute malicious code (such as a particular browser version or specific software installed on your computer). It's also possible that not all of the site pages are infected.
However, you should not ignore warnings of a potential threat. If you still need to go to the site, use a cached copy or take other security measures.
You can find more information about how malicious code ends up on pages and how to protect your site from infection in the Yandex.Webmaster Help.