That impact is now a little larger. Researchers from Graz University of Technology, including one of the original Meltdown discoverers, Daniel Gruss, have described NetSpectre: a fully remote attack based on Spectre. With NetSpectre, an attacker can remotely read the memory of a victim system without running any code on that system.
All the variants of the Spectre attacks follow a common set of principles. Each processor has an architectural behavior (the documented behavior that describes how the instructions work and that programmers depend on to write their programs) and a microarchitectural behavior (the way an actual implementation of the architecture behaves). These can diverge in subtle ways.
Read more: Ars Technica