This paper studies information flows via tuning channels in the presence of automatic memory management. We construct a series of example attacks that illustrate that garbage collectors form a shared resource that can be used to reliably leak sensitive information at a rate of up to 1 byte/sec on a contemporary general-purpose computer. The created channel is also observable across a network connection in a datacenter-like setting. We subsequently present a design of automatic memory management that is provably resilient against such attacks.