unpacker

noun

1. One who, or that which, unpacks.

   “One great advantage of professional unpacking is that the unpackers take away all the wrapping and cartons […]”

2. A software program that decompresses code or data.

   “All packed malware consists of the unpacker code and packed data, which typically look like random data. The benefit of packed malware, from a malicious author's point of view, is that it cannot be analyzed until it is properly unpacked.”