Starting from 2009, when AGS penalty, focused on punishing low quality sites usually created for selling SEO links, was introduced, Yandex began taking actions against link sellers. Typical symptoms of AGS were de-indexing of majority of pages of the affected website.
In 2014 AGS penalty evolved and instead of removing pages from the search index, Yandex started decreasing the TIC of the affected sites to zero, making them absolutely uninteresting to both existing and potential link buyers.
This week Yandex has announced [in Russian] yet another update to their AGS penalty. From now on AGS will also negatively affect organic rankings of the websites caught selling SEO links. At the same time TIC will continue being decreased to zero. The new AGS penalty can be applied to any site, regardless of its quality and authority.