Researchers have uncovered a new attack technique which can alter the memory of virtual machines in the cloud. The team explained that hackers could use the technique to crack the keys of secured VMs or install malicious code without it being noticed.
Using FFS, the attacker rents a VM on the same host as their chosen victim. They then write a memory page which they know exists on the vulnerable memory location and let it de-duplicate. The identical pages, with the same information, will merge in order to save capacity and be stored in the same part of memory of the physical computer. This allows the hacker to change information in the general memory of the computer.
https://thestack.com/cloud/2016/08/12/cloud-hacking-trick-allows-undetectable-changes-to-vm-memory/
https://linux.slashdot.org/story/16/08/14/0038226/researchers-warn-linux-vendors-about-cloud-memory-hacking-trick