ECB Securities Markets Programme
Officially, the ECB has started to purchase securities under the Securities Markets Programme (SMP) to address "the severe tensions in certain market segments which have been hampering the monetary policy transmission mechanism". Source: ECB
Some would argue that this is rather more than just guaranteeing the transmission of monetary policy. Below you find a graph showing the levels of securities purchased under the SMP. The data is updated on each Wednesday at 6pm CET.