I received an email that Yandex found an malware on my website.

Email subject: "Yandex Search found malware on your website"

Body: "Some of the pages on your website may pose a threat to your visitor's computer security. The number of potentially harmful pages is 8. You can view the details of our malware scan at URLHERE"

and on that URL is:
Yandex has detected malware on this site that may harm your computer or gain access to your personal information.
but no details on which URLs are infected and what kind of infection.

So i tried to scan my site by Sucuri scanner here: http://sitecheck.sucuri.net/ and it confirmed that only Yandex has an issue with my site.

On Yandex infected page (http://yandex.com/infected?url=XXX) i can see they are using Sophos.com antivirus solution, so i contacted Sophos asking for blacklisting details and they said:

If you think that this site is being blocked incorrectly, please submit a website reassessment request to our Sophos Labs for analysis..

Sophos reports that a website is blocked or has access restricted
http://www.sophos.com/en-us/support/...se/119440.aspx
and on that page i found this link:
https://secure2.sophos.com/en-us/thr...t-request.aspx

so i filled the form and submitted

PS: one can also register Yandex account (https://webmaster.yandex.com/) to read more details about blacklisting, but i did not tried it.