On the campaign settings page, find the Blocked sites and ad exchanges section under the advanced settings, and enter the site domains, mobile app IDs, or names of ad exchanges that you want to block from serving your ads (combined maximum of 1000).
On the Statistics page in the “By site” report, choose sites in the list and block them in the Action list.
If you add a particular site to the blocked list, campaign ads won't be served on either content pages of this site or search results for it. If you block impressions for a particular ad exchange, campaign ads won't be served on any of the sites in this ad exchange. However, if a site from a blocked ad exchange is in the YAN or another ad exchange and you did not set an individual block for this site, then impressions will continue on this site.
You can see on which platforms your ads are being served in the Report Wizard. The Ad exchanges section shows the name of the exchange where an ad was served. If the impression did not occur on an ad exchange, Yandex and YAN is shown.
Disabling impressions may result in losing a potential audience that you could have attracted and gained customers from.