The move from hardware middleboxes to software net-work functions, as advocated by NFV, has proven morechallenging than expected. Developing new NFs remains a tedious process, with developers frequently having to re-discover and reapply the same set of optimizations, while current techniques for safely running multiple NFs (using VMs or containers) incur high performance overheads. In this paper we describe NetBricks, a new NFV framework that aims to improve both the building and running of NFs. For building NFs we take inspiration from databases and modern data analytics frameworks (e.g.,Spark andMap Reduce) and build a framework with a small set of customizable network processing elements. To improve execution performance, NetBricks builds on safe languages and runtimes to provide isolation in software, rather than relying on hardware isolation. NetBricks provides memory isolation comparable to VMs, without the associated performance penalties. To provide efficient I/O, we introducea novel technique called zero-copy software isolation.